The lengths of two opposite sides of a square are decreased by 40% while the lengths of the other two sides are increased by 60% to form a rectangle. By what percent does the square's area decrease?

The original area = s^2

The new area is (s) (1 - .40) * (s ) (1 + .60) =

s^2 ( .60) (1.60) =

.96s^2

The area decreases by 1 - .96 = .04 = 4%