If the radius of a circle is decreased by 30%, then what is the decrease in the area of the circle?
Let radius of circle = $$r=10$$ cm
=> Area of circle = $$A=\pi r^2=\pi(10)^2=100\pi$$ $$cm^2$$
If the radius of a circle is decreased by 30%, new radius = $$r'=10-(\frac{30}{100}\times10)$$
= $$10-3=7$$ cm
=> New area = $$A'=\pi(7)^2=49\pi$$ $$cm^2$$
$$\therefore$$ Decrease in area of circle = $$\frac{(100\pi-49\pi)}{100\pi}\times100$$
= $$51\%$$
=> Ans - (A)
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