If the radius of a circle be reduced by 50%. Its area is reduced by?

• A. 39.5%
• B. 31.5%
• C. 34.5%
• D. 65.5%

Answer: (C)

Original area = ? x (r/2)2 = ?r2/4Reduction in area = ? r2 - 3? r2/4? Reduction per cent = [ 3?r2/4 x 4/(?r2) x 100 ] %= 75%