Because the overlapping shadow area is 1/3 of a triangle.

The area of a is 3a.

Because the area of overlapping shadow part is 2/5 of B triangle.

The area of b is 2.5a

Because the sum of the areas of two triangles a and b is s.

3a+2.5a=S

a=2/ 1 1S

A = 6/11sb = 5/1/s The shadow is 2/11s.

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