If the radius of a circle is increased by 10 percent, its area will increase by

A10%

B100%

C20%

D21% ✓ Correct

Correct answer: (D) 21%

Explanation

The area increases by 21%.

Area is proportional to the square of the radius.

New radius factor = 1.1, so area factor = 1.1^2.

1.1^2 = 1.21.

Increase = (1.21 - 1) x 100 = 21%.

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