Question 58

If radius of a circle is decreased by 11%, then the total decrease in the area of the circle is given as:

Solution

Initially Area = $$\pi r^2$$

After 11% decrements of the radius,

r1 = r $$\times \frac{88}{100} = 0.89r$$

Area = $$\pi (0.88r)^2 = \pi \times 0.7921r^2 $$

Total decrease in the area of the circle = $$\frac{\pi r^2 - 0.7921\pi r^2}{ \pi r^2} \times 100$$ = 20.79%

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