Difference between revisions of "2024 AMC 8 Problems/Problem 11"
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-Benedict T (countmath1) | -Benedict T (countmath1) | ||
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| + | ==Video Solution (easy to digest) by Power Solve== | ||
| + | https://www.youtube.com/watch?v=2UIVXOB4f0o | ||
==Video Solution by Math-X (First understand the problem!!!)== | ==Video Solution by Math-X (First understand the problem!!!)== | ||
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~Math-X | ~Math-X | ||
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==Video Solution 3 by SpreadTheMathLove== | ==Video Solution 3 by SpreadTheMathLove== | ||
https://www.youtube.com/watch?v=RRTxlduaDs8 | https://www.youtube.com/watch?v=RRTxlduaDs8 | ||
Revision as of 19:53, 26 January 2024
Contents
Problem
The coordinates of 
are 
, 
, and 
, with 
. The area of is 12. What is the value of 
?
![[asy] draw((3,11)--(11,7)--(5,7)--(3,11)); dot((5,7)); label("$A(5,7)$",(5,7),S); dot((11,7)); label("$B(11,7)$",(11,7),S); dot((3,11)); label("$C(3,y)$",(3,11),NW); [/asy]](http://latex.artofproblemsolving.com/3/a/1/3a1150ef27a4bba82b5f1aa665dc3e1dbe92d9f8.png)
Solution 1
The triangle has base 
which means its height satisfies
![\[\dfrac{6h}{2}=3h=12.\]](http://latex.artofproblemsolving.com/e/4/4/e448c160a210aadf166e977d28c622077d4e0ddf.png)
This means that 
so the answer is 
Solution 2
![[asy] size(10cm); draw((5,7)--(11,7)--(3,11)--cycle); draw((3,11)--(3,7)--(5,7),red); draw((3,7.5)--(3.5,7.5)--(3.5,7)); label("$A(5,7)$", (5,7),S); label("$B(11,7)$", (11,7),S); label("$C(3,y)$", (3,11),W); label("$D(3,7)$", (3,7),SW); [/asy]](http://latex.artofproblemsolving.com/6/c/3/6c3d5e8cefbc0744689ea5ca762f90f5209701e9.png)
Label point 
as the point at which 
. We now have ![$[\triangle ABC] = [\triangle BCD] - [\triangle ACD]$](http://latex.artofproblemsolving.com/f/3/0/f308cc469812756561fc3e1e8503d82e6b1c9e6a.png)
, where the brackets denote areas. On the righthand side, both of these triangles are right, so we can just compute the two sides of each triangle. The two side lengths of 
are 
and 
. The two side lengths of 
are and 
Now,
![\[[\triangle ABC] = 12 = \frac{1}{2}\cdot (y-7)\cdot 8 - \frac{1}{2}\cdot (y-7)\cdot 2 = 3(y-7)\]](http://latex.artofproblemsolving.com/f/7/d/f7dcf7c67e31a3176ece6003c89c42b7d320ba2d.png)
Dividing by 
gives 
so 
-Benedict T (countmath1)
Video Solution (easy to digest) by Power Solve
https://www.youtube.com/watch?v=2UIVXOB4f0o
Video Solution by Math-X (First understand the problem!!!)
~Math-X
