The lengths of two opposite sides of a square are decreased by 40% while the lengths of the other two sides are increased by 50% to form a rectangle. By what percent does the square's area decrease?

Question

it would be great if someone could help me on this :)

Answer 1

s represents the starting size of the sides

s² represents the starting area

0.6s and 1.5s represents the new sides

(0.6s)(1.5s) represents the new are

(0.6s)(1.5s) = 0.9s²

The new square is nine-tenth the area of the original.