单选题
If the radius of a circle is increased by 40%, how much will the area increase?
【正确答案】
E
【答案解析】A circle with radius r has area πr
2
. If the radius increases 40% from r to 1.4r, the area will increase to π(1.4r)
2
=π(1.4r)(1.4r)=1.96πr
2
, an increase of 96%.