If the radius of a circle is decreased by 50%, find the percentage decrease in its area.  Choose the correct answer: A) 25 % B) 50 % C) 75 % D) 95 % E) none of them

Rationale: "let original radius = r . new radius = ( 50 / 100 ) r = ( r / 2 ) original area = 22 / 7 ( r ) 2 = and new area =  ( ( r / 2 ) ) 2 = (  ( r ) 2 ) / 4 decrease in area = ( ( 3 ( 22 / 7 ) ( r ) 2 ) / 4 x ( 1 / ( 22 / 7 ) ( r ) 2 ) x 100 ) % = 75 % answer is c ."
Answer: C