Difference between revisions of "2014 AIME I Problems/Problem 13"
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<cmath>\sqrt{85}\rightarrow 34\implies \{4\sqrt{85}/5,18\sqrt{85}/5,12\sqrt{85}/5,14\sqrt{85}/5\}\implies\textcolor{red}{54.4,1101.6,489.6,666.4}</cmath> | <cmath>\sqrt{85}\rightarrow 34\implies \{4\sqrt{85}/5,18\sqrt{85}/5,12\sqrt{85}/5,14\sqrt{85}/5\}\implies\textcolor{red}{54.4,1101.6,489.6,666.4}</cmath> | ||
− | The three viable answers here are <math>272,306,850</math>. Since the areas add up to <math>1360</math> parts, probably the answer should be <math>\boxed{850}</math>. And perhaps MAA wants a high answer at the end of the AIME :). | + | The three viable answers here are <math>272,306,850</math>. Since the areas add up to <math>1360</math> parts, probably the answer should be <math>\boxed{850}</math>, a multiple of <math>5</math>. And perhaps MAA wants a high answer at the end of the AIME :). |
== See also == | == See also == | ||
{{AIME box|year=2014|n=I|num-b=12|num-a=14}} | {{AIME box|year=2014|n=I|num-b=12|num-a=14}} | ||
{{MAA Notice}} | {{MAA Notice}} |
Revision as of 13:05, 14 February 2016
Contents
Problem 13
On square , points , and lie on sides and respectively, so that and . Segments and intersect at a point , and the areas of the quadrilaterals and are in the ratio Find the area of square .
Solution
Notice that . This means passes through the centre of the square.
Draw with on , on such that and intersects at the centre of the square .
Let the area of the square be . Then the area of and the area of . This is because is perpendicular to (given in the problem), so is also perpendicular to . These two orthogonal lines also pass through the center of the square, so they split it into 4 congruent quadrilaterals.
Let the side length of the square be .
Draw and intersects at . .
The area of , so the area of .
Let . Then
Consider the area of .
Thus, .
Solving , we get .
Therefore, the area of
Strategy
, a multiple of . Therefore the of the "hypotenuse" of a triangle with slope must be a multiple of . All of these triples are primitive:
The sides of the square could either be the longer leg or the shorter leg. Substituting :
The three viable answers here are . Since the areas add up to parts, probably the answer should be , a multiple of . And perhaps MAA wants a high answer at the end of the AIME :).
See also
2014 AIME I (Problems • Answer Key • Resources) | ||
Preceded by Problem 12 |
Followed by Problem 14 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 | ||
All AIME Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.