if radius of a circle is reduced by 10%,then how much % of its area will be reduced?  Choose the correct choice
A) 10 % B) 19 % C) 20 % D) 36 % E) 30 %

Rationale: let initial radius = a then , area = π a ^ 2 . new radius = 90 % of a = 9 a / 10 . new area = π * 81 a ^ 2 / 100 = 81 / 100 π a ^ 2 reduce in area = [ π a ^ 2 - 81 / 100 π a ^ 2 ] = 19 / 100 π a ^ 2 % reduce = [ ( 19 * π a ^ 2 / 100 ) * ( 1 * 100 / π a ^ 2 ) ] % = 19 % answer b
Answer: B