Difference between revisions of "1998 AHSME Problems"
Lord.of.AMC (talk | contribs) (→Problem 5) |
|||
Line 131: | Line 131: | ||
The figure shown is the union of a circle and two semicircles of diameters <math>a</math> and <math>b</math>, all of whose centers are collinear. The ratio of the area, of the shaded region to that of the unshaded region is | The figure shown is the union of a circle and two semicircles of diameters <math>a</math> and <math>b</math>, all of whose centers are collinear. The ratio of the area, of the shaded region to that of the unshaded region is | ||
− | + | [asy] | |
+ | unitsize(1cm); | ||
+ | defaultpen(fontsize(10pt)+linewidth(.8pt)); | ||
+ | fill(Arc((1/3,0),2/3,0,180)--reverse(Arc((-2/3,0),1/3,180,360))--reverse(Arc((0,0),1,0,180))--cycle,mediumgray); | ||
+ | draw(unitcircle); | ||
+ | draw(Arc((-2/3,0),1/3,360,180)); | ||
+ | draw(Arc((1/3,0),2/3,0,180)); | ||
+ | label("<math>a</math>",(-2/3,0)); | ||
+ | label("<math>b</math>",(1/3,0)); | ||
+ | draw((-2/3+1/15,0)--(-1/3,0),EndArrow(4)); | ||
+ | draw((-2/3-1/15,0)--(-1,0),EndArrow(4)); | ||
+ | draw((1/3+1/15,0)--(1,0),EndArrow(4)); | ||
+ | draw((1/3-1/15,0)--(-1/3,0),EndArrow(4));[/asy] | ||
<math> \mathrm{(A) \ } \sqrt{\frac ab} \qquad \mathrm{(B) \ }\frac ab \qquad \mathrm{(C) \ } \frac{a^2}{b^2} \qquad \mathrm{(D) \ }\frac{a+b}{2b} \qquad \mathrm{(E) \ } \frac{a^2 + 2ab}{b^2 + 2ab}</math> | <math> \mathrm{(A) \ } \sqrt{\frac ab} \qquad \mathrm{(B) \ }\frac ab \qquad \mathrm{(C) \ } \frac{a^2}{b^2} \qquad \mathrm{(D) \ }\frac{a+b}{2b} \qquad \mathrm{(E) \ } \frac{a^2 + 2ab}{b^2 + 2ab}</math> |
Revision as of 12:07, 11 July 2010
Contents
- 1 Problem 1
- 2 Problem 2
- 3 Problem 3
- 4 Problem 4
- 5 Problem 5
- 6 Problem 6
- 7 Problem 7
- 8 Problem 8
- 9 Problem 9
- 10 Problem 10
- 11 Problem 11
- 12 Problem 12
- 13 Problem 13
- 14 Problem 14
- 15 Problem 15
- 16 Problem 16
- 17 Problem 17
- 18 Problem 18
- 19 Problem 19
- 20 Problem 20
- 21 Problem 21
- 22 Problem 22
- 23 Problem 23
- 24 Problem 24
- 25 Problem 25
- 26 Problem 26
- 27 Problem 27
- 28 Problem 28
- 29 Problem 29
- 30 Problem 30
- 31 See also
Problem 1
Each of the sides of five congruent rectangles is labeled with an integer, as shown above. These five rectangles are placed, without rotating or reflecting, in positions through
so that the labels on coincident sides are equal.
An image is supposed to go here. You can help us out by creating one and editing it in. Thanks.
Which of the rectangles is in position ?
Problem 2
Letters and
represent four different digits selected from
If
is an integer that is as large as possible, what is the value of
?
Problem 3
If and
are digits for which
\hline
&\ \texttt{c 7 3} \end{tabular}$ (Error compiling LaTeX. Unknown error_msg)then
Problem 4
Define to mean
, where
. What is the value of
![$\left[[60,30,90],[2,1,3],[10,5,15]\right]?$](http://latex.artofproblemsolving.com/d/2/c/d2cf272c97594ab2ba19c593e6899385689f28e6.png)
Problem 5
If what is the value of
?
Problem 6
If is written as a product of two positive integers whose difference is as small as possible, then the difference is
Problem 7
If , then
Problem 8
A square with sides of length is divided into two congruent trapezoids and a pentagon, which have equal areas, by joining the center of the square with points on three of the sides, as shown. Find
, the length of the longer parallel side of each trapezoid.
![[asy] pointpen = black; pathpen = black; D(unitsquare); D((0,0)); D((1,0)); D((1,1)); D((0,1)); D(D((.5,.5))--D((1,.5))); D(D((.17,1))--(.5,.5)--D((.17,0))); MP("x",(.58,1),N); [/asy]](http://latex.artofproblemsolving.com/6/d/6/6d64e011eb1d7812da21a5f3cd62791c42186299.png)
Problem 9
A speaker talked for sixty minutes to a full auditorium. Twenty percent of the audience heard the entire talk and ten percent slept through the entire talk. Half of the remainder heard one third of the talk and the other half heard two thirds of the talk. What was the average number of minutes of the talk heard by members of the audience?
Problem 10
A large square is divided into a small square surrounded by four congruent rectangles as shown. The perimter of each of the congruent rectangles is . What is the area of the large square?
![[asy] D((0,0)--(7,0)--(7,7)--(0,7)--cycle); D((1,0)--(1,6)); D((0,6)--(6,6)); D((1,1)--(7,1)); D((6,7)--(6,1)); [/asy]](http://latex.artofproblemsolving.com/b/2/1/b21c0ca175a9058df3e5a45c3fddfad5d1ee2e97.png)
Problem 11
Let be a rectangle. How many circles in the plane of
have a diameter both of whose endpoints are vertices of
?
Problem 12
How many different prime numbers are factors of if
![$\log_2 ( \log_3 ( \log_5 (\log_ 7 N))) = 11?$](http://latex.artofproblemsolving.com/3/e/2/3e299a9c249c24f7ece706fabc28efdbb48b77cd.png)
Problem 13
Walter rolls four standard six-sided dice and finds that the product of the numbers of the upper faces is . Which of he following could not be the sum of the upper four faces?
Problem 14
A parabola has vertex of and has two
intercepts, one positive, and one negative. If this parabola is the graph of
which of
and
must be positive?
Problem 15
A regular hexagon and an equilateral triangle have equal areas. What is the ratio of the length of a side of the triangle to the length of a side of the hexagon?
Problem 16
The figure shown is the union of a circle and two semicircles of diameters and
, all of whose centers are collinear. The ratio of the area, of the shaded region to that of the unshaded region is
[asy]
unitsize(1cm);
defaultpen(fontsize(10pt)+linewidth(.8pt));
fill(Arc((1/3,0),2/3,0,180)--reverse(Arc((-2/3,0),1/3,180,360))--reverse(Arc((0,0),1,0,180))--cycle,mediumgray);
draw(unitcircle);
draw(Arc((-2/3,0),1/3,360,180));
draw(Arc((1/3,0),2/3,0,180));
label("",(-2/3,0));
label("
",(1/3,0));
draw((-2/3+1/15,0)--(-1/3,0),EndArrow(4));
draw((-2/3-1/15,0)--(-1,0),EndArrow(4));
draw((1/3+1/15,0)--(1,0),EndArrow(4));
draw((1/3-1/15,0)--(-1/3,0),EndArrow(4));[/asy]
Problem 17
Let be a function with the two properties:
- (a) for any two real numbers
and
,
, and
- (b)
What is the value of
Problem 18
A right circular cone of volume , a right circular cylinder of volume
, and a sphere of volume
all have the same radius, and the common height of the cone and the cylinder is equal to the diameter of the sphere. Then
Problem 19
How many triangles have area and vertices at
and
for some angle
?
Problem 20
Three cards, each with a positive integer written on it, are lying face-down on a table. Casey, Stacy, and Tracy are told that
- (a) the numbers are all different,
- (b) they sum to
, and
- (c) they are in increasing order, left to right.
First, Casey looks at the number on the leftmost card and says, "I don't have enough information to determine the other two numbers." Then Tracy looks at the number on the rightmost card and says, "I don't have enough information to determine the other two numbers." Finally, Stacy looks at the number on the middle card and says, "I don't have enough information to determine the other two numbers." Assume that each person knows that the other two reason perfectly and hears their comments. What number is on the middle card?
Problem 21
In an -meter race, Sunny is exactly
meters ahead of Windy when Sunny finishes the race. The next time they race, Sunny sportingly starts
meters behind Windy, who is at the starting line. Both runners run at the same constant speed as they did in the first race. How many meters ahead is Sunny when Sunny finishes the second race?
Problem 22
What is the value of the expression
![$\frac {1}{\log_{2}100!} + \frac {1}{\log_{3}100!} + \frac {1}{\log_{4}100!} + \cdots + \frac {1}{\log_{100}100!}$](http://latex.artofproblemsolving.com/f/9/6/f963dbb8e8305d39c07140f98eaf5651cce543da.png)
Problem 23
The graphs of and
intersect when
satisfies
, and for no other values of
. Find
.
Problem 24
Call a -digit telephone number
memorable if the prefix sequence
is exactly the same as either of the sequences
or
(possibly both). Assuming that each
can be any of the ten decimal digits
, the number of difference memorable telephone numbers is
Problem 25
A piece of graph paper is folded once so that is matched with
, and
is matched with
. Find
.
Problem 26
In quadrilateral , it is given that
, angles
and
are right angles,
, and
. Then
Problem 27
A cube is composed of twenty-seven
cubes. The big cube is ‘tunneled’ as follows: First the six
cubes which make up the center of each face as well as the center
cube are removed as shown. Second, each of the twenty remaining
cubes is diminished in the same way. That is, the center facial unit cubes as well as each center cube are removed. The surface area of the final figure is
Problem 28
In triangle , angle
is a right angle and
. Point
is located on
so that angle
is twice angle
. If
, then
, where
and
are relatively prime positive integers. Find
.
Problem 29
A point in the plane is called a lattice point if both
and
are integers. The area of the largest square that contains exactly three lattice points in its interior is closest to
Problem 30
For each positive integer , let
![$a_n = \frac{(n+9)!}{(n-1)!}$](http://latex.artofproblemsolving.com/e/f/4/ef41faf809af6fe77c9547ed59aaee0f23a7709e.png)
Let denote the smallest positive integer for which the rightmost nonzero digit of
is odd. The rightmost nonzero digit of
is