The radius of a sphere is increased by 10%. The surface area increases by? Select the correct option:	A) 21%	B) 31%	C) 41%	D) 51%	E) none of these
Since 4 x pi x radius x radius = surface area.   Therefore, net % change in area   = ( x + y + xy/100) %   = [10 + 10 + (10 x 10)/100]% or 21%.   21%NSWER:21%
<result>A</result>
The radius of a sphere is increased by 10%. The surface area increases by?