2000 AIME I Problems/Problem 4

Revision as of 20:23, 2 March 2008 by Watermaximillion (talk | contribs) (Solution)

Problem

The diagram shows a rectangle that has been dissected into nine non-overlapping squares. Given that the width and the height of the rectangle are relatively prime positive integers, find the perimeter of the rectangle.

[asy]draw((0,0)--(69,0)--(69,61)--(0,61)--(0,0));draw((36,0)--(36,36)--(0,36)); draw((36,33)--(69,33));draw((41,33)--(41,61));draw((25,36)--(25,61)); draw((34,36)--(34,45)--(25,45)); draw((36,36)--(36,38)--(34,38)); draw((36,38)--(41,38)); draw((34,45)--(41,45));[/asy]

Solution

Call the squares' side lengths from smallest to largest $a_1,\ldots,a_9$, and let $l,w$ represent the dimensions of the rectangle.

The picture shows that $a_1+a_2= a_3$, $a_1 + a_3 = a_4$, $a_3 + a_4 = a_5$, $a_4 + a_5 = a_6$, $a_2 + a_3 + a_5 = a_7$, $a_2 + a_7 = a_8$, $a_1 + a_4 + a_6 = a_9$, and $a_6 + a_9 = a_7 + a_8$.

With a bit of trial and error and some arithmetic, we can use the last equation to find that $5a_1 = 2a_2$; without loss of generality, let $a_1 = 2$. Then solving gives $a_9 = 36$, $a_6=25$, $a_8 = 33$, which gives us $l=61,w=69$ (relatively prime), and the perimeter is $2(61)+2(69)=\boxed{260}$.

See also

2000 AIME I (ProblemsAnswer KeyResources)
Preceded by
Problem 3
Followed by
Problem 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All AIME Problems and Solutions
Invalid username
Login to AoPS