Elementary Geometry for College Students (7th Edition)

Lets take the initial base of a rectangle be b and the height be h Base is increased by 20% of b therefore final Base = 1.2 b The altitude is increased by 30 % of h Final altitude =1.3 h The area of rectangle whose base has length b and altitude has length h is given by A = bh Initial area of rectangle = bh Final area of rectangle = (1.2b) * (1.3h) = 1.56bh Increase in area of rectangle in percentage = $\frac{final area - initial area}{initial area}$ * 100 =$\frac{1.56bh - bh}{bh}$ * 100 =$\frac{0.56bh}{bh}$ * 100 = 0.56 * 100 = 56% therefore 56% area is increased