If each side of a square is increased by 25%, find the percentage change in its area.

• A. 16.25%
• B. 12.25%
• C. 56.25%
• D. 36.25%

Answer: (C)

Let each side of the square be a. Then, area = . a 2 New side = 125 a 100 = 5 a 4 . New area =  5 a 4 2  =  25 a 2 16   Increase in area =  25 a 2 16 - a 2 = 9 a 2 16 Increase% =  9 a 2 16 * 1 a 2 * 100  % = 56.25%.