Maths / Comparing Quantities / Percentage Change

QUESTION
 

If radius of a circle is increassed by 10% then area of the circle will be increased by

OPTIONS
A. 

50%

B. 

15%

C. 

21%

D. 

20%

Right Option : C

EXPLANATION
Explain TypeExplanation Content
Text

Let the radius = r

increase = 10% of r=0.1r

New Radius = 1.1r

large Original: Area = pi X r^2

large dpi{120} fn_jvn large New: Area = pi X (1.1r)^2 = 1.21pi Xr^2

large Increase= 1.21pi Xr^2 -pi X r^2 = 0.21 pi r^2

large Percentage : Increase= frac{increase}{original}X 100=frac{0.21pi r^2}{pi r^2} X 100

=21 %

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