Can you find the area of the triangle shown?

Geometry Level 2

Find the area of the triangle shown.


The answer is 44.

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2 solutions

The area of the triangle is equal to the area of the rectangle circumscribing the triangle minus the sum of the areas of the three small triangles. We have

A = 10 ( 12 ) 1 2 [ 8 ( 12 ) + 2 ( 8 ) + 10 ( 4 ) ] = 120 1 2 ( 152 ) = 44 A=10(12)-\dfrac{1}{2}[8(12)+2(8)+10(4)]=120-\dfrac{1}{2}(152)=\boxed{44}

Les Schumer
Jun 18, 2020

To simplify the arithmetic, consider the lower left vertex to be at ( 0 , 0 ) (0,0) , then apply the Shoelace Formula.

A r e a = 1 2 d e t ( 0 0 1 10 4 1 8 12 1 ) Area = \frac{1}{2}det\left({\begin{array}{ccc} 0 & 0 & 1 \\ 10 & 4 & 1 \\ 8 & 12 & 1 \end{array}}\right)

A r e a = 1 2 [ 12 ( 10 ) 8 ( 4 ) ] = 1 2 [ 88 ] = 44 Area = \frac{1}{2}[12(10)-8(4)] = \frac{1}{2}[88] = \fbox{44}

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