Question 83

If the radius of a circle is increased by 31% its area increases by ______.

Solution

Let radius = 10 cm

=> Area of circle = $$\pi (10)^2 = 100 \pi$$ sq. cm

If radius is increased by 31%, => New radius = $$10 + \frac{31}{100} \times 10$$ = 13.1 cm

New area = $$\pi (13.1)^2 = 171.61 \pi$$ sq. cm

=> % increase in area = $$\frac{171.61 - 100}{100} \times 100$$

= 71.61 %

=> Ans - (D)

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