Question 834817
Q:
The radius of a circle was increased by 25 percent. By what percent did the area of the circle increase?
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Answer:
Area of Circle, A = {{{pi*r^2}}}
If old radius, {{{r[old]}}} = 1, then new radius, {{{r[new]}}} = 1.25 and 
percent increase = {{{(pi*(1.25^2) - pi*(1^2))/(pi*(1^2))}}}, divide the numerator and denominator by {{{pi}}}
percent increase = {{{(1.25^2- 1^2)/1^2}}} = 0.5625 or 56.25%