Difference between revisions of "2016 AMC 12A Problems/Problem 9"
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==Solution== | ==Solution== | ||
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| + | Let <math>s</math> be the side length of the small squares. | ||
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| + | The diagonal of the big square can be written in two ways: <math>\sqrt{2} and </math>s \sqrt{2} + s + s \sqrt{2}<math>. | ||
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| + | Solving for </math>s<math>, we get </math>s = \frac{4 - \sqrt{2}}{7}<math>, so our answer is </math>4 + 7 \Rightarrow \boxed{\textbf{(E)} 11}$ | ||
Revision as of 14:20, 4 February 2016
Problem 9
The five small shaded squares inside this unit square are congruent and have disjoint interiors. The midpoint of each side of the middle square coincides with one of the vertices of the other four small squares as shown. The common side length is 
, where 
and 
are positive integers. What is 
?
![[asy] real x=.369; draw((0,0)--(0,1)--(1,1)--(1,0)--cycle); filldraw((0,0)--(0,x)--(x,x)--(x,0)--cycle, gray); filldraw((0,1)--(0,1-x)--(x,1-x)--(x,1)--cycle, gray); filldraw((1,1)--(1,1-x)--(1-x,1-x)--(1-x,1)--cycle, gray); filldraw((1,0)--(1,x)--(1-x,x)--(1-x,0)--cycle, gray); filldraw((.5,.5-x*sqrt(2)/2)--(.5+x*sqrt(2)/2,.5)--(.5,.5+x*sqrt(2)/2)--(.5-x*sqrt(2)/2,.5)--cycle, gray); [/asy]](http://latex.artofproblemsolving.com/8/2/2/822d7c29853b8e549e65edc3bf9cf6445b799d11.png)
Solution
Let 
be the side length of the small squares.
The diagonal of the big square can be written in two ways: 
s \sqrt{2} + s + s \sqrt{2}$.
Solving for$ (Error compiling LaTeX. Unknown error_msg)s
s = \frac{4 - \sqrt{2}}{7}
4 + 7 \Rightarrow \boxed{\textbf{(E)} 11}$
