Difference between revisions of "2000 AMC 10 Problems/Problem 5"
(New page: (a) Clearly does not change, as <math>MN=\frac{1}{2}AB</math>. Since <math>AB</math> does not change, neither does <math>MN</math>. (b) Obviously, the perimetar changes. (c) The area cle...) |
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− | + | ==Problem== | |
− | + | Points <math>M</math> and <math>N</math> are the midpoints of sides <math>PA</math> and <math>PB</math> of <math>\triangle PAB</math>. As <math>P</math> moves along a line that is parallel to side <math>AB</math>, how many of the four quantities listed below change? | |
− | ( | + | (a) the length of the segment <math>MN</math> |
− | ( | + | (b) the perimeter of <math>\triangle PAB</math> |
− | Only <math>1</math> changes, so B. | + | (c) the area of <math>\triangle PAB</math> |
+ | |||
+ | (d) the area of trapezoid <math>ABNM</math> | ||
+ | |||
+ | <asy> | ||
+ | draw((2,0)--(8,0)--(6,4)--cycle); | ||
+ | draw((4,2)--(7,2)); | ||
+ | draw((1,4)--(9,4),Arrows); | ||
+ | label("$A$",(2,0),SW); | ||
+ | label("$B$",(8,0),SE); | ||
+ | label("$M$",(4,2),W); | ||
+ | label("$N$",(7,2),E); | ||
+ | label("$P$",(6,4),N); | ||
+ | </asy> | ||
+ | |||
+ | <math>\mathrm{(A)}\ 0 \qquad\mathrm{(B)}\ 1 \qquad\mathrm{(C)}\ 2 \qquad\mathrm{(D)}\ 3 \qquad\mathrm{(E)}\ 4</math> | ||
+ | |||
+ | ==Solution== | ||
+ | |||
+ | (a) Clearly <math>AB</math> does not change, and <math>MN=\frac{1}{2}AB</math>, so <math>MN</math> doesn't change either. | ||
+ | |||
+ | (b) Obviously, the perimeter changes. For example, imagine if P was extremely far to the left. | ||
+ | |||
+ | (c) The area clearly doesn't change, as both the base <math>AB</math> and its corresponding height remain the same. | ||
+ | |||
+ | (d) The bases <math>AB</math> and <math>MN</math> do not change, and neither does the height, so the area of the trapezoid remains the same. | ||
+ | |||
+ | Only <math>1</math> quantity changes, so the correct answer is <math>\boxed{\text{B}}</math>. | ||
+ | |||
+ | ==See Also== | ||
+ | |||
+ | {{AMC10 box|year=2000|num-b=4|num-a=6}} | ||
+ | {{MAA Notice}} | ||
+ | [[Category:Introductory Geometry Problems]] |
Revision as of 15:33, 19 April 2021
Problem
Points and are the midpoints of sides and of . As moves along a line that is parallel to side , how many of the four quantities listed below change?
(a) the length of the segment
(b) the perimeter of
(c) the area of
(d) the area of trapezoid
Solution
(a) Clearly does not change, and , so doesn't change either.
(b) Obviously, the perimeter changes. For example, imagine if P was extremely far to the left.
(c) The area clearly doesn't change, as both the base and its corresponding height remain the same.
(d) The bases and do not change, and neither does the height, so the area of the trapezoid remains the same.
Only quantity changes, so the correct answer is .
See Also
2000 AMC 10 (Problems • Answer Key • Resources) | ||
Preceded by Problem 4 |
Followed by Problem 6 | |
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 AMC 10 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.