If the radius of a circle is decreased by 50% , find the percentage decrease in its area.

• A. 65%
• B. 25%
• C. 75%
• D. 35%

Answer: (C)

let original radius = r and  new radius = (50/100) r = r/2   original area =  ?r 2  and new area =  ? r / 2 2   decrease in area =  3 ?r 2 / 4 * 1 ?r 2  *100 = 75%