Question

A rectangle measures 20cm by 15cm.If each dimension is increased by 2.5cm, by what percentage is

1. the perimeter of the rectangle increased
2. the area of the rectangle is increased

Answer 1

1. Original perimeter  = 2(20+15) =70
                Increase = 4 × 2.5 =10              
                     %Inc = ¹⁰/₇₀ × 100 =14.29% 
2. Original area  =20×15=300
   Area with increase =(2.5 +20) (2.5 + 15) = 393.75
   Increase= 93.75                                                     
        % inc= 93.75 ×100 =31.25%                          
                    300