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Difference between revisions of "1999 AMC 8 Problems"

(Problem 7)
 
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 +
{{AMC8 Problems|year=1999|}}
 
==Problem 1==
 
==Problem 1==
  
<math>(6?3) + 4 - (2 - 1) = 5.</math> To make this statement true, the question mark between the 6 and the 3 should be replaced by
+
<math>(6?3) + 4 - (2 - 1) = 5</math> To make this statement true, the question mark between the 6 and the 3 should be replaced by
  
 
<math>\text{(A)} \div \qquad \text{(B)}\ \times \qquad \text{(C)} + \qquad \text{(D)}\ - \qquad \text{(E)}\ \text{None of these}</math>
 
<math>\text{(A)} \div \qquad \text{(B)}\ \times \qquad \text{(C)} + \qquad \text{(D)}\ - \qquad \text{(E)}\ \text{None of these}</math>
Line 9: Line 10:
 
== Problem 2 ==
 
== Problem 2 ==
  
What is the degree measure of the smaller angle formed by the hands of a clock at 10 o'clock?
+
What is the degree measure of the smaller angle formed by the hands of a clock at 10 o clock?
  
{{image}}
+
<asy>
 +
draw(circle((0,0),2));
 +
dot((0,0));
 +
for(int i = 0; i < 12; ++i)
 +
{
 +
dot(2*dir(30*i));
 +
}
 +
 
 +
label("$3$",2*dir(0),W);
 +
label("$2$",2*dir(30),WSW);
 +
label("$1$",2*dir(60),SSW);
 +
label("$12$",2*dir(90),S);
 +
label("$11$",2*dir(120),SSE);
 +
label("$10$",2*dir(150),ESE);
 +
label("$9$",2*dir(180),E);
 +
label("$8$",2*dir(210),ENE);
 +
label("$7$",2*dir(240),NNE);
 +
label("$6$",2*dir(270),N);
 +
label("$5$",2*dir(300),NNW);
 +
label("$4$",2*dir(330),WNW);
 +
</asy>
  
 
<math>\text{(A)}\ 30 \qquad \text{(B)}\ 45 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 75 \qquad \text{(E)}\ 90</math>
 
<math>\text{(A)}\ 30 \qquad \text{(B)}\ 45 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 75 \qquad \text{(E)}\ 90</math>
Line 29: Line 50:
 
The diagram shows the miles traveled by bikers Alberto and Bjorn. After four hours, about how many more miles has Alberto biked than Bjorn?
 
The diagram shows the miles traveled by bikers Alberto and Bjorn. After four hours, about how many more miles has Alberto biked than Bjorn?
  
{{image}}
+
<asy>
 +
for (int a = 0; a < 6; ++a)
 +
{
 +
for (int b = 0; b < 6; ++b)
 +
{
 +
dot((4*a,3*b));
 +
}
 +
}
 +
draw((0,0)--(20,0)--(20,15)--(0,15)--cycle);
 +
draw((0,0)--(16,12));
 +
draw((0,0)--(16,9));
 +
 
 +
label(rotate(30)*"Bjorn",(12,6.75),SE);
 +
label(rotate(37)*"Alberto",(11,8.25),NW);
 +
 
 +
label("$0$",(0,0),S);
 +
label("$1$",(4,0),S);
 +
label("$2$",(8,0),S);
 +
label("$3$",(12,0),S);
 +
label("$4$",(16,0),S);
 +
label("$5$",(20,0),S);
 +
label("$0$",(0,0),W);
 +
label("$15$",(0,3),W);
 +
label("$30$",(0,6),W);
 +
label("$45$",(0,9),W);
 +
label("$60$",(0,12),W);
 +
label("$75$",(0,15),W);
 +
 
 +
label("H",(6,-2),S);
 +
label("O",(8,-2),S);
 +
label("U",(10,-2),S);
 +
label("R",(12,-2),S);
 +
label("S",(14,-2),S);
 +
 
 +
label("M",(-4,11),N);
 +
label("I",(-4,9),N);
 +
label("L",(-4,7),N);
 +
label("E",(-4,5),N);
 +
label("S",(-4,3),N);
 +
</asy>
  
 
<math>\text{(A)}\ 15 \qquad \text{(B)}\ 20 \qquad \text{(C)}\ 25 \qquad \text{(D)}\ 30 \qquad \text{(E)}\ 35</math>
 
<math>\text{(A)}\ 15 \qquad \text{(B)}\ 20 \qquad \text{(C)}\ 25 \qquad \text{(D)}\ 30 \qquad \text{(E)}\ 35</math>
Line 37: Line 97:
 
==Problem 5==
 
==Problem 5==
  
A rectangular garden 50 feet long and 10 feet wide is enclosed by a fence. To make the garden larger, while using the same fence, its shape is changed to a square. By how many square feet does this enlarge the garden?
+
A rectangular garden 60 feet long and 20 feet wide is enclosed by a fence. To make the garden larger, while using the same fence, its shape is changed to a square. By how many square feet does this enlarge the garden?
  
 
<math>\text{(A)}\ 100 \qquad \text{(B)}\ 200 \qquad \text{(C)}\ 300 \qquad \text{(D)}\ 400 \qquad \text{(E)}\ 500</math>
 
<math>\text{(A)}\ 100 \qquad \text{(B)}\ 200 \qquad \text{(C)}\ 300 \qquad \text{(D)}\ 400 \qquad \text{(E)}\ 500</math>
Line 45: Line 105:
 
==Problem 6==
 
==Problem 6==
  
Bo, Coe, Flo, Joe, and Moe have different amounts of money. Neither Jo nor Bo has as much money as Flo. Both Bo and Coe have more than Moe. Jo has more than Moe, but less than Bo. Who has the least amount of money?
+
Bo, Coe, Flo, Joe, and Moe have different amounts of money. Neither Joe nor Bo has as much money as Flo. Both Bo and Coe have more than Moe. Joe has more than Moe, but less than Bo. Who has the least amount of money?
  
 
<math>\text{(A)}\ \text{Bo} \qquad \text{(B)}\ \text{Coe} \qquad \text{(C)}\ \text{Flo} \qquad \text{(D)}\ \text{Joe} \qquad \text{(E)}\ \text{Moe}</math>
 
<math>\text{(A)}\ \text{Bo} \qquad \text{(B)}\ \text{Coe} \qquad \text{(C)}\ \text{Flo} \qquad \text{(D)}\ \text{Joe} \qquad \text{(E)}\ \text{Moe}</math>
Line 63: Line 123:
 
Six squares are colored, front and back, (R = red, B = blue, O = orange, Y = yellow, G = green, and W = white). They are hinged together as shown, then folded to form a cube. The face opposite the white face is
 
Six squares are colored, front and back, (R = red, B = blue, O = orange, Y = yellow, G = green, and W = white). They are hinged together as shown, then folded to form a cube. The face opposite the white face is
  
{{image}}
+
<asy>
 +
draw((0,2)--(1,2)--(1,1)--(2,1)--(2,0)--(3,0)--(3,1)--(4,1)--(4,2)--(2,2)--(2,3)--(0,3)--cycle);
 +
draw((1,3)--(1,2)--(2,2)--(2,1)--(3,1)--(3,2));
 +
label("R",(.5,2.3),N);
 +
label("B",(1.5,2.3),N);
 +
label("G",(1.5,1.3),N);
 +
label("Y",(2.5,1.3),N);
 +
label("W",(2.5,.3),N);
 +
label("O",(3.5,1.3),N);
 +
</asy>
  
 
<math>\text{(A)}\ \text{B} \qquad \text{(B)}\ \text{G} \qquad \text{(C)}\ \text{O} \qquad \text{(D)}\ \text{R} \qquad \text{(E)}\ \text{Y}</math>
 
<math>\text{(A)}\ \text{B} \qquad \text{(B)}\ \text{G} \qquad \text{(C)}\ \text{O} \qquad \text{(D)}\ \text{R} \qquad \text{(E)}\ \text{Y}</math>
Line 73: Line 142:
 
Three flower beds overlap as shown. Bed A has 500 plants, bed B has 450 plants, and bed C has 350 plants. Beds A and B share 50 plants, while beds A and C share 100. The total number of plants is
 
Three flower beds overlap as shown. Bed A has 500 plants, bed B has 450 plants, and bed C has 350 plants. Beds A and B share 50 plants, while beds A and C share 100. The total number of plants is
  
{{image}}
+
<asy>
 +
draw((0,0)--(3,0)--(3,1)--(0,1)--cycle);
 +
draw(circle((.3,-.1),.7));
 +
draw(circle((2.8,-.2),.8));
 +
label("A",(1.3,.5),N);
 +
label("B",(3.1,-.2),S);
 +
label("C",(.6,-.2),S);
 +
</asy>
  
 
<math>\text{(A)}\ 850 \qquad \text{(B)}\ 1000 \qquad \text{(C)}\ 1150 \qquad \text{(D)}\ 1300 \qquad \text{(E)}\ 1450</math>
 
<math>\text{(A)}\ 850 \qquad \text{(B)}\ 1000 \qquad \text{(C)}\ 1150 \qquad \text{(D)}\ 1300 \qquad \text{(E)}\ 1450</math>
Line 91: Line 167:
 
Each of the five numbers 1, 4, 7, 10, and 13 is placed in one of the five squares so that the sum of the three numbers in the horizontal row equals the sum of the three numbers in the vertical column. The largest possible value for the horizontal or vertical sum is
 
Each of the five numbers 1, 4, 7, 10, and 13 is placed in one of the five squares so that the sum of the three numbers in the horizontal row equals the sum of the three numbers in the vertical column. The largest possible value for the horizontal or vertical sum is
  
{{image}}
+
<asy>
 +
draw((0,0)--(3,0)--(3,1)--(0,1)--cycle);
 +
draw((1,-1)--(2,-1)--(2,2)--(1,2)--cycle);
 +
</asy>
  
 
<math>\text{(A)}\ 20 \qquad \text{(B)}\ 21 \qquad \text{(C)}\ 22 \qquad \text{(D)}\ 24 \qquad \text{(E)}\ 30</math>
 
<math>\text{(A)}\ 20 \qquad \text{(B)}\ 21 \qquad \text{(C)}\ 22 \qquad \text{(D)}\ 24 \qquad \text{(E)}\ 30</math>
Line 107: Line 186:
 
==Problem 13==
 
==Problem 13==
  
The average age of the 40 members of a computer science camp is 17 years. There are 20 girls, 15 boys, and 5 adults. If the average age of the girls is 15 and the average age of the boys is 16, what is the average age of the adults?
+
The average age of the 40 members of a computer science camp is 17 years. There are 20 girls, 15 boys, and 5 adults. If the average age of the girl is 15 and the average age of the boys is 16, what is the average age of the adults ?
  
 
<math>\text{(A)}\ 26 \qquad \text{(B)}\ 27 \qquad \text{(C)}\ 28 \qquad \text{(D)}\ 29 \qquad \text{(E)}\ 30</math>
 
<math>\text{(A)}\ 26 \qquad \text{(B)}\ 27 \qquad \text{(C)}\ 28 \qquad \text{(D)}\ 29 \qquad \text{(E)}\ 30</math>
  
[[1999 AMC 8 Problems/Problem 13|Solution]]
+
[[1999 AMC 8 Problems/Problem 13|Solution]
  
 
==Problem 14==
 
==Problem 14==
Line 117: Line 196:
 
In trapezoid <math>ABCD</math>, the sides <math>AB</math> and <math>CD</math> are equal. The perimeter of <math>ABCD</math> is
 
In trapezoid <math>ABCD</math>, the sides <math>AB</math> and <math>CD</math> are equal. The perimeter of <math>ABCD</math> is
  
{{image}}
+
<asy>
 +
draw((0,0)--(4,3)--(12,3)--(16,0)--cycle);
 +
draw((4,3)--(4,0),dashed);
 +
draw((3.2,0)--(3.2,.8)--(4,.8));
 +
 
 +
label("$A$",(0,0),SW);
 +
label("$B$",(4,3),NW);
 +
label("$C$",(12,3),NE);
 +
label("$D$",(16,0),SE);
 +
label("$8$",(8,3),N);
 +
label("$16$",(8,0),S);
 +
label("$3$",(4,1.5),E);
 +
</asy>
  
 
<math>\text{(A)}\ 27 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 32 \qquad \text{(D)}\ 34 \qquad \text{(E)}\ 48</math>
 
<math>\text{(A)}\ 27 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 32 \qquad \text{(D)}\ 34 \qquad \text{(E)}\ 48</math>
Line 141: Line 232:
 
[[1999 AMC 8 Problems/Problem 16|Solution]]
 
[[1999 AMC 8 Problems/Problem 16|Solution]]
  
==Cookies For a Crowd==
+
==Problem 17==
  
 
Problems 17, 18, and 19 refer to the following:
 
Problems 17, 18, and 19 refer to the following:
  
<center>
+
At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: <math>1\frac{1}{2}</math> cups flour, <math>2</math> eggs, <math>3</math> tablespoons butter, <math>\frac{3}{4}</math> cups sugar, and <math>1</math> package of chocolate drops. They will make only full recipes, not partial recipes.
At Central Middle School the 108 students who take the AMC<math>\to</math>8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: <math>1\frac{1}{2}</math> cups flour, <math>2</math> eggs, <math>3</math> tablespoons butter, <math>\frac{3}{4}</math> cups sugar, and <math>1</math> package of chocolate drops. They will make only full recipes, not partial recipes.
 
</center>
 
 
 
===Problem 17===
 
  
 
Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.)
 
Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.)
Line 157: Line 244:
 
[[1999 AMC 8 Problems/Problem 17|Solution]]
 
[[1999 AMC 8 Problems/Problem 17|Solution]]
  
===Problem 18===
+
==Problem 18==
 +
 
 +
Problems 17, 18, and 19 refer to the following:
 +
 
 +
At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: <math>1\frac{1}{2}</math> cups flour, <math>2</math> eggs, <math>3</math> tablespoons butter, <math>\frac{3}{4}</math> cups sugar, and <math>1</math> package of chocolate drops. They will make only full recipes, not partial recipes.
  
 
They learn that a big concert is scheduled for the same night and attendance will be down 25%. How many recipes of cookies should they make for their smaller party?
 
They learn that a big concert is scheduled for the same night and attendance will be down 25%. How many recipes of cookies should they make for their smaller party?
Line 165: Line 256:
 
[[1999 AMC 8 Problems/Problem 18|Solution]]
 
[[1999 AMC 8 Problems/Problem 18|Solution]]
  
===Problem 19===
+
==Problem 19==
 +
Problems 17, 18, and 19 refer to the following:
 +
 
 +
At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: <math>1\frac{1}{2}</math> cups flour, <math>2</math> eggs, <math>3</math> tablespoons butter, <math>\frac{3}{4}</math> cups sugar, and <math>1</math> package of chocolate drops. They will make only full recipes, not partial recipes.
  
 
The drummer gets sick. The concert is cancelled. Walter and Gretel must make enough pans of cookies to supply 216 cookies. There are 8 tablespoons in a stick of butter. How many sticks of butter will be needed? (Some butter may be left over, of course.)
 
The drummer gets sick. The concert is cancelled. Walter and Gretel must make enough pans of cookies to supply 216 cookies. There are 8 tablespoons in a stick of butter. How many sticks of butter will be needed? (Some butter may be left over, of course.)
Line 179: Line 273:
 
Which of the following is the front view for the stack map in Fig. 4?
 
Which of the following is the front view for the stack map in Fig. 4?
  
{{image}}
+
<asy>
 +
unitsize(24);
 +
 
 +
draw((0,0)--(2,0)--(2,2)--(0,2)--cycle);
 +
draw((1,0)--(1,2));
 +
draw((0,1)--(2,1));
 +
 
 +
draw((5,0)--(7,0)--(7,1)--(20/3,4/3)--(20/3,13/3)--(19/3,14/3)--(16/3,14/3)--(16/3,11/3)--(13/3,11/3)--(13/3,2/3)--cycle);
 +
draw((20/3,13/3)--(17/3,13/3)--(17/3,10/3)--(14/3,10/3)--(14/3,1/3));
 +
draw((20/3,10/3)--(17/3,10/3)--(17/3,7/3)--(20/3,7/3));
 +
draw((17/3,7/3)--(14/3,7/3));
 +
draw((7,1)--(6,1)--(6,2)--(5,2)--(5,0));
 +
draw((5,1)--(6,1)--(6,0));
 +
draw((20/3,4/3)--(6,4/3));
 +
draw((17/3,13/3)--(16/3,14/3));
 +
draw((17/3,10/3)--(16/3,11/3));
 +
draw((14/3,10/3)--(13/3,11/3));
 +
draw((5,2)--(13/3,8/3));
 +
draw((5,1)--(13/3,5/3));
 +
draw((6,2)--(17/3,7/3));
 +
 
 +
draw((9,0)--(11,0)--(11,4)--(10,4)--(10,3)--(9,3)--cycle);
 +
draw((11,3)--(10,3)--(10,0));
 +
draw((11,2)--(9,2));
 +
draw((11,1)--(9,1));
 +
 
 +
draw((13,0)--(16,0)--(16,2)--(13,2)--cycle);
 +
draw((13,1)--(16,1));
 +
draw((14,0)--(14,2));
 +
draw((15,0)--(15,2));
 +
 
 +
label("Figure 1",(1,0),S);
 +
label("Figure 2",(17/3,0),S);
 +
label("Figure 3",(10,0),S);
 +
label("Figure 4",(14.5,0),S);
 +
 
 +
label("$1$",(1.5,.2),N);
 +
label("$2$",(.5,.2),N);
 +
label("$3$",(.5,1.2),N);
 +
label("$4$",(1.5,1.2),N);
 +
 
 +
label("$1$",(13.5,.2),N);
 +
label("$3$",(14.5,.2),N);
 +
label("$1$",(15.5,.2),N);
 +
label("$2$",(13.5,1.2),N);
 +
label("$2$",(14.5,1.2),N);
 +
label("$4$",(15.5,1.2),N);
 +
</asy>
 +
 
 +
<br /> <br />
 +
 
 +
<asy>
 +
unitsize(18);
 +
draw((0,0)--(3,0)--(3,2)--(1,2)--(1,4)--(0,4)--cycle);
 +
draw((0,3)--(1,3));
 +
draw((0,2)--(1,2)--(1,0));
 +
draw((0,1)--(3,1));
 +
draw((2,0)--(2,2));
 +
 
 +
draw((5,0)--(8,0)--(8,4)--(7,4)--(7,3)--(6,3)--(6,2)--(5,2)--cycle);
 +
draw((8,3)--(7,3)--(7,0));
 +
draw((8,2)--(6,2)--(6,0));
 +
draw((8,1)--(5,1));
 +
 
 +
draw((10,0)--(12,0)--(12,4)--(11,4)--(11,3)--(10,3)--cycle);
 +
draw((12,3)--(11,3)--(11,0));
 +
draw((12,2)--(10,2));
 +
draw((12,1)--(10,1));
 +
 
 +
draw((14,0)--(17,0)--(17,4)--(16,4)--(16,2)--(14,2)--cycle);
 +
draw((17,3)--(16,3));
 +
draw((17,2)--(16,2)--(16,0));
 +
draw((17,1)--(14,1));
 +
draw((15,0)--(15,2));
 +
 
 +
draw((19,0)--(22,0)--(22,4)--(20,4)--(20,1)--(19,1)--cycle);
 +
draw((22,3)--(20,3));
 +
draw((22,2)--(20,2));
 +
draw((22,1)--(20,1)--(20,0));
 +
draw((21,0)--(21,4));
 +
 
 +
label("(A)",(1.5,0),S);
 +
label("(B)",(6.5,0),S);
 +
label("(C)",(11,0),S);
 +
label("(D)",(15.5,0),S);
 +
label("(E)",(20.5,0),S);
 +
</asy>
  
 
[[1999 AMC 8 Problems/Problem 20|Solution]]
 
[[1999 AMC 8 Problems/Problem 20|Solution]]
Line 187: Line 367:
 
The degree measure of angle <math>A</math> is
 
The degree measure of angle <math>A</math> is
  
{{image}}
+
<asy>
 +
unitsize(12);
 +
draw((0,0)--(20,0)--(1,-10)--(9,5)--(18,-8)--cycle);
 +
draw(arc((1,-10),(1+19/sqrt(461),-10+10/sqrt(461)),(25/17,-155/17),CCW));
 +
draw(arc((19/3,0),(19/3-8/17,-15/17),(22/3,0),CCW));
 +
draw(arc((900/83,-400/83),(900/83+19/sqrt(461),-400/83+10/sqrt(461)),(900/83 - 9/sqrt(97),-400/83 + 4/sqrt(97)),CCW));
 +
label(rotate(30)*"$40^\circ$",(2,-8.9),ENE);
 +
label("$100^\circ$",(21/3,-2/3),SE);
 +
label("$110^\circ$",(900/83,-317/83),NNW);
 +
label("$A$",(0,0),NW);
 +
</asy>
  
 
<math>\text{(A)}\ 20 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 35 \qquad \text{(D)}\ 40 \qquad \text{(E)}\ 45</math>
 
<math>\text{(A)}\ 20 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 35 \qquad \text{(D)}\ 40 \qquad \text{(E)}\ 45</math>
Line 205: Line 395:
 
Square <math>ABCD</math> has sides of length 3. Segments <math>CM</math> and <math>CN</math> divide the square's area into three equal parts. How long is segment <math>CM</math>?
 
Square <math>ABCD</math> has sides of length 3. Segments <math>CM</math> and <math>CN</math> divide the square's area into three equal parts. How long is segment <math>CM</math>?
  
{{image}}
+
<asy>
 +
pair A,B,C,D,M,N;
 +
A = (0,0);
 +
B = (0,3);
 +
C = (3,3);
 +
D = (3,0);
 +
M = (0,1);
 +
N = (1,0);
 +
draw(A--B--C--D--cycle);
 +
draw(M--C--N);
 +
label("$A$",A,SW);
 +
label("$M$",M,W);
 +
label("$B$",B,NW);
 +
label("$C$",C,NE);
 +
label("$D$",D,SE);
 +
label("$N$",N,S);
 +
</asy>
  
 
<math>\text{(A)}\ \sqrt{10} \qquad \text{(B)}\ \sqrt{12} \qquad \text{(C)}\ \sqrt{13} \qquad \text{(D)}\ \sqrt{14} \qquad \text{(E)}\ \sqrt{15}</math>
 
<math>\text{(A)}\ \sqrt{10} \qquad \text{(B)}\ \sqrt{12} \qquad \text{(C)}\ \sqrt{13} \qquad \text{(D)}\ \sqrt{14} \qquad \text{(E)}\ \sqrt{15}</math>
Line 215: Line 421:
 
When <math>1999^{2000}</math> is divided by <math>5</math>, the remainder is  
 
When <math>1999^{2000}</math> is divided by <math>5</math>, the remainder is  
  
<math>\text{(A)}\ 4 \qquad \text{(B)}\ 3 \qquad \text{(C)}\ 2 \qquad \text{(D)}\ 1 \qquad \text{(E)}\ 0</math>
+
<math>\text{(A)}\ 0 \qquad \text{(B)}\ 1 \qquad \text{(C)}\ 2 \qquad \text{(D)}\ 3 \qquad \text{(E)}\ 4</math>
  
 
[[1999 AMC 8 Problems/Problem 24|Solution]]
 
[[1999 AMC 8 Problems/Problem 24|Solution]]
Line 223: Line 429:
 
Points <math>B</math>, <math>D</math>, and <math>J</math> are midpoints of the sides of right triangle <math>ACG</math>. Points <math>K</math>, <math>E</math>, <math>I</math> are midpoints of the sides of triangle <math>JDG</math>, etc. If the dividing and shading process is done 100 times (the first three are shown) and <math>AC=CG=6</math>, then the total area of the shaded triangles is nearest
 
Points <math>B</math>, <math>D</math>, and <math>J</math> are midpoints of the sides of right triangle <math>ACG</math>. Points <math>K</math>, <math>E</math>, <math>I</math> are midpoints of the sides of triangle <math>JDG</math>, etc. If the dividing and shading process is done 100 times (the first three are shown) and <math>AC=CG=6</math>, then the total area of the shaded triangles is nearest
  
{{image}}
+
<asy>
 +
draw((0,0)--(6,0)--(6,6)--cycle);
 +
draw((3,0)--(3,3)--(6,3));
 +
draw((4.5,3)--(4.5,4.5)--(6,4.5));
 +
draw((5.25,4.5)--(5.25,5.25)--(6,5.25));
 +
fill((3,0)--(6,0)--(6,3)--cycle,black);
 +
fill((4.5,3)--(6,3)--(6,4.5)--cycle,black);
 +
fill((5.25,4.5)--(6,4.5)--(6,5.25)--cycle,black);
 +
 
 +
label("$A$",(0,0),SW);
 +
label("$B$",(3,0),S);
 +
label("$C$",(6,0),SE);
 +
label("$D$",(6,3),E);
 +
label("$E$",(6,4.5),E);
 +
label("$F$",(6,5.25),E);
 +
label("$G$",(6,6),NE);
 +
label("$H$",(5.25,5.25),NW);
 +
label("$I$",(4.5,4.5),NW);
 +
label("$J$",(3,3),NW);
 +
label("$K$",(4.5,3),S);
 +
label("$L$",(5.25,4.5),S);
 +
</asy>
  
 
<math>\text{(A)}\ 6 \qquad \text{(B)}\ 7 \qquad \text{(C)}\ 8 \qquad \text{(D)}\ 9 \qquad \text{(E)}\ 10</math>
 
<math>\text{(A)}\ 6 \qquad \text{(B)}\ 7 \qquad \text{(C)}\ 8 \qquad \text{(D)}\ 9 \qquad \text{(E)}\ 10</math>
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* [[AMC 8 Problems and Solutions]]
 
* [[AMC 8 Problems and Solutions]]
 
* [[Mathematics competition resources]]
 
* [[Mathematics competition resources]]
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 +
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{{MAA Notice}}

Latest revision as of 15:39, 9 November 2024

1999 AMC 8 (Answer Key)
Printable versions: WikiAoPS ResourcesPDF

Instructions

  1. This is a 25-question, multiple choice test. Each question is followed by answers marked A, B, C, D and E. Only one of these is correct.
  2. You will receive 1 point for each correct answer. There is no penalty for wrong answers.
  3. No aids are permitted other than plain scratch paper, writing utensils, ruler, and erasers. In particular, graph paper, compass, protractor, calculators, computers, smartwatches, and smartphones are not permitted. Rules
  4. Figures are not necessarily drawn to scale.
  5. You will have 40 minutes working time to complete the test.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Problem 1

$(6?3) + 4 - (2 - 1) = 5$ To make this statement true, the question mark between the 6 and the 3 should be replaced by

$\text{(A)} \div \qquad \text{(B)}\ \times \qquad \text{(C)} + \qquad \text{(D)}\ - \qquad \text{(E)}\ \text{None of these}$

Solution

Problem 2

What is the degree measure of the smaller angle formed by the hands of a clock at 10 o clock?

[asy] draw(circle((0,0),2)); dot((0,0)); for(int i = 0; i < 12; ++i) { dot(2*dir(30*i)); }  label("$3$",2*dir(0),W); label("$2$",2*dir(30),WSW); label("$1$",2*dir(60),SSW); label("$12$",2*dir(90),S); label("$11$",2*dir(120),SSE); label("$10$",2*dir(150),ESE); label("$9$",2*dir(180),E); label("$8$",2*dir(210),ENE); label("$7$",2*dir(240),NNE); label("$6$",2*dir(270),N); label("$5$",2*dir(300),NNW); label("$4$",2*dir(330),WNW); [/asy]

$\text{(A)}\ 30 \qquad \text{(B)}\ 45 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 75 \qquad \text{(E)}\ 90$

Solution

Problem 3

Which triplet of numbers has a sum NOT equal to 1?

$\text{(A)}\ (1/2,1/3,1/6) \qquad \text{(B)}\ (2,-2,1) \qquad \text{(C)}\ (0.1,0.3,0.6) \qquad \text{(D)}\ (1.1,-2.1,1.0) \qquad \text{(E)}\ (-3/2,-5/2,5)$

Solution

Problem 4

The diagram shows the miles traveled by bikers Alberto and Bjorn. After four hours, about how many more miles has Alberto biked than Bjorn?

[asy] for (int a = 0; a < 6; ++a) { for (int b = 0; b < 6; ++b) { dot((4*a,3*b)); } } draw((0,0)--(20,0)--(20,15)--(0,15)--cycle); draw((0,0)--(16,12)); draw((0,0)--(16,9));  label(rotate(30)*"Bjorn",(12,6.75),SE); label(rotate(37)*"Alberto",(11,8.25),NW);  label("$0$",(0,0),S); label("$1$",(4,0),S); label("$2$",(8,0),S); label("$3$",(12,0),S); label("$4$",(16,0),S); label("$5$",(20,0),S); label("$0$",(0,0),W); label("$15$",(0,3),W); label("$30$",(0,6),W); label("$45$",(0,9),W); label("$60$",(0,12),W); label("$75$",(0,15),W);  label("H",(6,-2),S); label("O",(8,-2),S); label("U",(10,-2),S); label("R",(12,-2),S); label("S",(14,-2),S);  label("M",(-4,11),N); label("I",(-4,9),N); label("L",(-4,7),N); label("E",(-4,5),N); label("S",(-4,3),N); [/asy]

$\text{(A)}\ 15 \qquad \text{(B)}\ 20 \qquad \text{(C)}\ 25 \qquad \text{(D)}\ 30 \qquad \text{(E)}\ 35$

Solution

Problem 5

A rectangular garden 60 feet long and 20 feet wide is enclosed by a fence. To make the garden larger, while using the same fence, its shape is changed to a square. By how many square feet does this enlarge the garden?

$\text{(A)}\ 100 \qquad \text{(B)}\ 200 \qquad \text{(C)}\ 300 \qquad \text{(D)}\ 400 \qquad \text{(E)}\ 500$

Solution

Problem 6

Bo, Coe, Flo, Joe, and Moe have different amounts of money. Neither Joe nor Bo has as much money as Flo. Both Bo and Coe have more than Moe. Joe has more than Moe, but less than Bo. Who has the least amount of money?

$\text{(A)}\ \text{Bo} \qquad \text{(B)}\ \text{Coe} \qquad \text{(C)}\ \text{Flo} \qquad \text{(D)}\ \text{Joe} \qquad \text{(E)}\ \text{Moe}$

Solution

Problem 7

The third exit on a highway is located at milepost 40 and the tenth exit is at milepost 160. There is a service center on the highway located three-fourths of the way from the third exit to the tenth exit. At what milepost would you expect to find this service center?

$\text{(A)}\ 90 \qquad \text{(B)}\ 100 \qquad \text{(C)}\ 110 \qquad \text{(D)}\ 120 \qquad \text{(E)}\ 130$

Solution

Problem 8

Six squares are colored, front and back, (R = red, B = blue, O = orange, Y = yellow, G = green, and W = white). They are hinged together as shown, then folded to form a cube. The face opposite the white face is

[asy] draw((0,2)--(1,2)--(1,1)--(2,1)--(2,0)--(3,0)--(3,1)--(4,1)--(4,2)--(2,2)--(2,3)--(0,3)--cycle); draw((1,3)--(1,2)--(2,2)--(2,1)--(3,1)--(3,2)); label("R",(.5,2.3),N); label("B",(1.5,2.3),N); label("G",(1.5,1.3),N); label("Y",(2.5,1.3),N); label("W",(2.5,.3),N); label("O",(3.5,1.3),N); [/asy]

$\text{(A)}\ \text{B} \qquad \text{(B)}\ \text{G} \qquad \text{(C)}\ \text{O} \qquad \text{(D)}\ \text{R} \qquad \text{(E)}\ \text{Y}$

Solution

Problem 9

Three flower beds overlap as shown. Bed A has 500 plants, bed B has 450 plants, and bed C has 350 plants. Beds A and B share 50 plants, while beds A and C share 100. The total number of plants is

[asy] draw((0,0)--(3,0)--(3,1)--(0,1)--cycle); draw(circle((.3,-.1),.7)); draw(circle((2.8,-.2),.8)); label("A",(1.3,.5),N); label("B",(3.1,-.2),S); label("C",(.6,-.2),S); [/asy]

$\text{(A)}\ 850 \qquad \text{(B)}\ 1000 \qquad \text{(C)}\ 1150 \qquad \text{(D)}\ 1300 \qquad \text{(E)}\ 1450$

Solution

Problem 10

A complete cycle of a traffic light takes 60 seconds. During each cycle the light is green for 25 seconds, yellow for 5 seconds, and red for 30 seconds. At a randomly chosen time, what is the probability that the light will NOT be green?

$\text{(A)}\ \frac{1}{4} \qquad \text{(B)}\ \frac{1}{3} \qquad \text{(C)}\ \frac{5}{12} \qquad \text{(D)}\ \frac{1}{2} \qquad \text{(E)}\ \frac{7}{12}$

Solution

Problem 11

Each of the five numbers 1, 4, 7, 10, and 13 is placed in one of the five squares so that the sum of the three numbers in the horizontal row equals the sum of the three numbers in the vertical column. The largest possible value for the horizontal or vertical sum is

[asy] draw((0,0)--(3,0)--(3,1)--(0,1)--cycle); draw((1,-1)--(2,-1)--(2,2)--(1,2)--cycle); [/asy]

$\text{(A)}\ 20 \qquad \text{(B)}\ 21 \qquad \text{(C)}\ 22 \qquad \text{(D)}\ 24 \qquad \text{(E)}\ 30$

Solution

Problem 12

The ratio of the number of games won to the number of games lost (no ties) by the Middle School Middies is $11/4$. To the nearest whole percent, what percent of its games did the team lose?

$\text{(A)}\ 24 \qquad \text{(B)}\ 27 \qquad \text{(C)}\ 36 \qquad \text{(D)}\ 45 \qquad \text{(E)}\ 73$

Solution

Problem 13

The average age of the 40 members of a computer science camp is 17 years. There are 20 girls, 15 boys, and 5 adults. If the average age of the girl is 15 and the average age of the boys is 16, what is the average age of the adults ?

$\text{(A)}\ 26 \qquad \text{(B)}\ 27 \qquad \text{(C)}\ 28 \qquad \text{(D)}\ 29 \qquad \text{(E)}\ 30$

[[1999 AMC 8 Problems/Problem 13|Solution]

Problem 14

In trapezoid $ABCD$, the sides $AB$ and $CD$ are equal. The perimeter of $ABCD$ is

[asy] draw((0,0)--(4,3)--(12,3)--(16,0)--cycle); draw((4,3)--(4,0),dashed); draw((3.2,0)--(3.2,.8)--(4,.8));  label("$A$",(0,0),SW); label("$B$",(4,3),NW); label("$C$",(12,3),NE); label("$D$",(16,0),SE); label("$8$",(8,3),N); label("$16$",(8,0),S); label("$3$",(4,1.5),E); [/asy]

$\text{(A)}\ 27 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 32 \qquad \text{(D)}\ 34 \qquad \text{(E)}\ 48$

Solution

Problem 15

Bicycle license plates in Flatville each contain three letters. The first is chosen from the set {C,H,L,P,R}, the second from {A,I,O}, and the third from {D,M,N,T}.

When Flatville needed more license plates, they added two new letters. The new letters may both be added to one set or one letter may be added to one set and one to another set. What is the largest possible number of ADDITIONAL license plates that can be made by adding two letters?

$\text{(A)}\ 24 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 36 \qquad \text{(D)}\ 40 \qquad \text{(E)}\ 60$

Solution

Problem 16

Tori's mathematics test had 75 problems: 10 arithmetic, 30 algebra, and 35 geometry problems. Although she answered 70% of the arithmetic, 40% of the algebra, and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% of the problems right. How many more problems would she have needed to answer correctly to earn a 60% passing grade?

$\text{(A)}\ 1 \qquad \text{(B)}\ 5 \qquad \text{(C)}\ 7 \qquad \text{(D)}\ 9 \qquad \text{(E)}\ 11$

Solution

Problem 17

Problems 17, 18, and 19 refer to the following:

At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: $1\frac{1}{2}$ cups flour, $2$ eggs, $3$ tablespoons butter, $\frac{3}{4}$ cups sugar, and $1$ package of chocolate drops. They will make only full recipes, not partial recipes.

Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.)

$\text{(A)}\ 1 \qquad \text{(B)}\ 2 \qquad \text{(C)}\ 5 \qquad \text{(D)}\ 7 \qquad \text{(E)}\ 15$

Solution

Problem 18

Problems 17, 18, and 19 refer to the following:

At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: $1\frac{1}{2}$ cups flour, $2$ eggs, $3$ tablespoons butter, $\frac{3}{4}$ cups sugar, and $1$ package of chocolate drops. They will make only full recipes, not partial recipes.

They learn that a big concert is scheduled for the same night and attendance will be down 25%. How many recipes of cookies should they make for their smaller party?

$\text{(A)}\ 6 \qquad \text{(B)}\ 8 \qquad \text{(C)}\ 9 \qquad \text{(D)}\ 10 \qquad \text{(E)}\ 11$

Solution

Problem 19

Problems 17, 18, and 19 refer to the following:

At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: $1\frac{1}{2}$ cups flour, $2$ eggs, $3$ tablespoons butter, $\frac{3}{4}$ cups sugar, and $1$ package of chocolate drops. They will make only full recipes, not partial recipes.

The drummer gets sick. The concert is cancelled. Walter and Gretel must make enough pans of cookies to supply 216 cookies. There are 8 tablespoons in a stick of butter. How many sticks of butter will be needed? (Some butter may be left over, of course.)

$\text{(A)}\ 5 \qquad \text{(B)}\ 6 \qquad \text{(C)}\ 7 \qquad \text{(D)}\ 8 \qquad \text{(E)}\ 9$

Solution

Problem 20

Figure 1 is called a "stack map." The numbers tell how many cubes are stacked in each position. Fig. 2 shows these cubes, and Fig. 3 shows the view of the stacked cubes as seen from the front.

Which of the following is the front view for the stack map in Fig. 4?

[asy] unitsize(24);  draw((0,0)--(2,0)--(2,2)--(0,2)--cycle); draw((1,0)--(1,2)); draw((0,1)--(2,1));  draw((5,0)--(7,0)--(7,1)--(20/3,4/3)--(20/3,13/3)--(19/3,14/3)--(16/3,14/3)--(16/3,11/3)--(13/3,11/3)--(13/3,2/3)--cycle); draw((20/3,13/3)--(17/3,13/3)--(17/3,10/3)--(14/3,10/3)--(14/3,1/3)); draw((20/3,10/3)--(17/3,10/3)--(17/3,7/3)--(20/3,7/3)); draw((17/3,7/3)--(14/3,7/3)); draw((7,1)--(6,1)--(6,2)--(5,2)--(5,0)); draw((5,1)--(6,1)--(6,0)); draw((20/3,4/3)--(6,4/3)); draw((17/3,13/3)--(16/3,14/3)); draw((17/3,10/3)--(16/3,11/3)); draw((14/3,10/3)--(13/3,11/3)); draw((5,2)--(13/3,8/3)); draw((5,1)--(13/3,5/3)); draw((6,2)--(17/3,7/3));  draw((9,0)--(11,0)--(11,4)--(10,4)--(10,3)--(9,3)--cycle); draw((11,3)--(10,3)--(10,0)); draw((11,2)--(9,2)); draw((11,1)--(9,1));  draw((13,0)--(16,0)--(16,2)--(13,2)--cycle); draw((13,1)--(16,1)); draw((14,0)--(14,2)); draw((15,0)--(15,2));  label("Figure 1",(1,0),S); label("Figure 2",(17/3,0),S); label("Figure 3",(10,0),S); label("Figure 4",(14.5,0),S);  label("$1$",(1.5,.2),N); label("$2$",(.5,.2),N); label("$3$",(.5,1.2),N); label("$4$",(1.5,1.2),N);  label("$1$",(13.5,.2),N); label("$3$",(14.5,.2),N); label("$1$",(15.5,.2),N); label("$2$",(13.5,1.2),N); label("$2$",(14.5,1.2),N); label("$4$",(15.5,1.2),N); [/asy]



[asy] unitsize(18); draw((0,0)--(3,0)--(3,2)--(1,2)--(1,4)--(0,4)--cycle); draw((0,3)--(1,3)); draw((0,2)--(1,2)--(1,0)); draw((0,1)--(3,1)); draw((2,0)--(2,2));  draw((5,0)--(8,0)--(8,4)--(7,4)--(7,3)--(6,3)--(6,2)--(5,2)--cycle); draw((8,3)--(7,3)--(7,0)); draw((8,2)--(6,2)--(6,0)); draw((8,1)--(5,1));  draw((10,0)--(12,0)--(12,4)--(11,4)--(11,3)--(10,3)--cycle); draw((12,3)--(11,3)--(11,0)); draw((12,2)--(10,2)); draw((12,1)--(10,1));  draw((14,0)--(17,0)--(17,4)--(16,4)--(16,2)--(14,2)--cycle); draw((17,3)--(16,3)); draw((17,2)--(16,2)--(16,0)); draw((17,1)--(14,1)); draw((15,0)--(15,2));  draw((19,0)--(22,0)--(22,4)--(20,4)--(20,1)--(19,1)--cycle); draw((22,3)--(20,3)); draw((22,2)--(20,2)); draw((22,1)--(20,1)--(20,0)); draw((21,0)--(21,4));  label("(A)",(1.5,0),S); label("(B)",(6.5,0),S); label("(C)",(11,0),S); label("(D)",(15.5,0),S); label("(E)",(20.5,0),S); [/asy]

Solution

Problem 21

The degree measure of angle $A$ is

[asy] unitsize(12); draw((0,0)--(20,0)--(1,-10)--(9,5)--(18,-8)--cycle); draw(arc((1,-10),(1+19/sqrt(461),-10+10/sqrt(461)),(25/17,-155/17),CCW)); draw(arc((19/3,0),(19/3-8/17,-15/17),(22/3,0),CCW)); draw(arc((900/83,-400/83),(900/83+19/sqrt(461),-400/83+10/sqrt(461)),(900/83 - 9/sqrt(97),-400/83 + 4/sqrt(97)),CCW)); label(rotate(30)*"$40^\circ$",(2,-8.9),ENE); label("$100^\circ$",(21/3,-2/3),SE); label("$110^\circ$",(900/83,-317/83),NNW); label("$A$",(0,0),NW); [/asy]

$\text{(A)}\ 20 \qquad \text{(B)}\ 30 \qquad \text{(C)}\ 35 \qquad \text{(D)}\ 40 \qquad \text{(E)}\ 45$

Solution

Problem 22

In a far-off land three fish can be traded for two loaves of bread and a loaf of bread can be traded for four bags of rice. How many bags of rice is one fish worth?

$\text{(A)}\ \frac{3}{8} \qquad \text{(B)}\ \frac{1}{2} \qquad \text{(C)}\ \frac{3}{4} \qquad \text{(D)}\ 2\frac{2}{3} \qquad \text{(E)}\ 3\frac{1}{3}$

Solution

Problem 23

Square $ABCD$ has sides of length 3. Segments $CM$ and $CN$ divide the square's area into three equal parts. How long is segment $CM$?

[asy] pair A,B,C,D,M,N; A = (0,0); B = (0,3); C = (3,3); D = (3,0); M = (0,1); N = (1,0); draw(A--B--C--D--cycle); draw(M--C--N); label("$A$",A,SW); label("$M$",M,W); label("$B$",B,NW); label("$C$",C,NE); label("$D$",D,SE); label("$N$",N,S); [/asy]

$\text{(A)}\ \sqrt{10} \qquad \text{(B)}\ \sqrt{12} \qquad \text{(C)}\ \sqrt{13} \qquad \text{(D)}\ \sqrt{14} \qquad \text{(E)}\ \sqrt{15}$

Solution

Problem 24

When $1999^{2000}$ is divided by $5$, the remainder is

$\text{(A)}\ 0 \qquad \text{(B)}\ 1 \qquad \text{(C)}\ 2 \qquad \text{(D)}\ 3 \qquad \text{(E)}\ 4$

Solution

Problem 25

Points $B$, $D$, and $J$ are midpoints of the sides of right triangle $ACG$. Points $K$, $E$, $I$ are midpoints of the sides of triangle $JDG$, etc. If the dividing and shading process is done 100 times (the first three are shown) and $AC=CG=6$, then the total area of the shaded triangles is nearest

[asy] draw((0,0)--(6,0)--(6,6)--cycle); draw((3,0)--(3,3)--(6,3)); draw((4.5,3)--(4.5,4.5)--(6,4.5)); draw((5.25,4.5)--(5.25,5.25)--(6,5.25)); fill((3,0)--(6,0)--(6,3)--cycle,black); fill((4.5,3)--(6,3)--(6,4.5)--cycle,black); fill((5.25,4.5)--(6,4.5)--(6,5.25)--cycle,black);  label("$A$",(0,0),SW); label("$B$",(3,0),S); label("$C$",(6,0),SE); label("$D$",(6,3),E); label("$E$",(6,4.5),E); label("$F$",(6,5.25),E); label("$G$",(6,6),NE); label("$H$",(5.25,5.25),NW); label("$I$",(4.5,4.5),NW); label("$J$",(3,3),NW); label("$K$",(4.5,3),S); label("$L$",(5.25,4.5),S); [/asy]

$\text{(A)}\ 6 \qquad \text{(B)}\ 7 \qquad \text{(C)}\ 8 \qquad \text{(D)}\ 9 \qquad \text{(E)}\ 10$

Solution

See also

1999 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
1998 AJHSME
Followed by
2000 AMC 8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions


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