Triangle area from triangle

Geometry Level 2


The answer is 48.

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2 solutions

Let the position coordinates of A , B , C A, B, C be ( b , c ) , ( 0 , 0 ) , ( a , 0 ) (b, c), (0,0),(a, 0) respectively.

Then those of K , L K, L are ( a + 2 b 4 , c 2 ) , ( 2 a + b 4 , c 4 ) (\frac{a+2b}{4},\frac{c}{2}),(\frac{2a+b}{4},\frac{c}{4}) respectively.

Hence, area of B K L \triangle {BKL} is

9 = 1 2 a + 2 b 4 × c 4 + 2 a + b 4 × ( c 2 ) = 3 a c 32 9=\frac{1}{2}|\frac{a+2b}{4}\times \frac{c}{4}+\frac{2a+b}{4}\times (-\frac{c}{2})|=\dfrac {3ac}{32}

\implies area of A B C \triangle {ABC} is

1 2 a c = 48 \dfrac {1}{2}ac=\boxed {48} .

thanks for you sir excellent

Aly Ahmed - 11 months, 1 week ago

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Thanks to you also for posting beautiful problems.

Aly Ahmed
Jul 10, 2020

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