UPSC CDS Math Area and Perimeter Questions

If each side of triangle is halved, then the new triangle will be similar to the original triangle. We know that the ratio of areas of two similar triangles = ratio of square of sides of two similar triangles.
Let A and a be the original and new areas of a triangle.

A

a

=(

2

1

)2=4
A=4a
Percentage decrease in area =

(4a−a)

4a

×100=75%