area of a triangle

Geometry Level pending

In the diagram above, relative lengths of some line segments are shown.

If the area of A B C = 126 \triangle ABC=126 , what is the area of E A D \triangle EAD ?


The answer is 28.8.

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1 solution

A A B C = 1 2 ( 2 y ) ( 5 x ) ( sin B ) A_{ABC}=\dfrac{1}{2}(2y)(5x)(\sin~B) \implies y x sin B = 126 5 yx \sin~B=\dfrac{126}{5}

A 1 = 1 2 ( y ) ( 2 x ) ( sin B ) = 126 5 A_1=\dfrac{1}{2}(y)(2x)( \sin~B)=\dfrac{126}{5}

A A B C = 1 2 ( 2 y ) ( 14 z ) ( sin A ) A_{ABC}=\dfrac{1}{2}(2y)(14z)(\sin~A) \implies y z sin A = 9 yz \sin~A=9

A 2 = 1 2 ( y ) ( 4 z ) ( sin A ) = 2 ( 9 ) = 18 A_2=\dfrac{1}{2}(y)(4z)(\sin~A)=2(9)=18

A A B C = 1 2 ( 5 x ) ( 14 z ) ( sin C ) A_{ABC}=\dfrac{1}{2}(5x)(14z)(\sin~C) \implies x z sin C = 18 5 xz \sin~C=\dfrac{18}{5}

A 3 = 1 2 ( 3 x ) ( 10 z ) ( sin C ) = 15 ( 18 5 ) = 54 A_3=\dfrac{1}{2}(3x)(10z)(\sin~C) = 15\left(\dfrac{18}{5}\right)=54

The area of E A D \triangle EAD is 126 126 5 18 54 = 144 5 = 126-\dfrac{126}{5}-18-54=\dfrac{144}{5}= 28.8 \color{#D61F06}\boxed{28.8}

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