Difference between revisions of "2016 AMC 12B Problems/Problem 10"
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By the Shoelace Theorem, the area of the quadrilateral is <math>2a^2 - 2b^2</math>, so <math>a^2 - b^2 = 8</math>. Since <math>a</math> and <math>b</math> are integers, <math>a = 3</math> and <math>b = 1</math>, so <math>a + b = \boxed{\textbf{(A)}\ 4}</math>. | By the Shoelace Theorem, the area of the quadrilateral is <math>2a^2 - 2b^2</math>, so <math>a^2 - b^2 = 8</math>. Since <math>a</math> and <math>b</math> are integers, <math>a = 3</math> and <math>b = 1</math>, so <math>a + b = \boxed{\textbf{(A)}\ 4}</math>. | ||
− | ==Video Solution by TheBeautyofMath | + | ==Video Solution by TheBeautyofMath== |
https://www.youtube.com/watch?v=Eq2A2TTahqU | https://www.youtube.com/watch?v=Eq2A2TTahqU | ||
with a second example of Shoelace Theorem done after this problem | with a second example of Shoelace Theorem done after this problem |
Revision as of 07:07, 19 February 2021
Problem
A quadrilateral has vertices ,
,
, and
, where
and
are integers with
. The area of
is
. What is
?
Solution
Note that the slope of is
and the slope of
is
. Hence,
and we can similarly prove that the other angles are right angles. This means that
is a rectangle. By distance formula we have
. Simplifying we get
. Thus
and
have to be a factor of 8. The only way for them to be factors of
and remain integers is if
and
. So the answer is
Solution by I_Dont_Do_Math
Solution 2
Solution by e_power_pi_times_i
By the Shoelace Theorem, the area of the quadrilateral is , so
. Since
and
are integers,
and
, so
.
Video Solution by TheBeautyofMath
https://www.youtube.com/watch?v=Eq2A2TTahqU with a second example of Shoelace Theorem done after this problem ~IceMatrix
See Also
2016 AMC 12B (Problems • Answer Key • Resources) | |
Preceded by Problem 9 |
Followed by Problem 11 |
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 12 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.