Question

if the radius of circle is decreased by 50%, what will be the percentage decrease in its area? ​

Answer 1

Answer:

Let radius was 2x .

So area will be

$= \pi {r}^{2} = \pi {(2x)}^{2} = 4\pi { {x}^{2} }$

When radius is decreased by 50% , New radius will be x . and new area

$= \pi {x}^{2}$

So % change

$y = \frac{4\pi {x}^{2} - \pi {x}^{2} }{4\pi {x}^{2} } \times 100 = 75\%$