Question

if the area of circle, whose radius is 5cm is increased to four times, then find the changed radius?​

Answer 1

Answer:

$area \: of \: a \: circle \: = \: \pi \: {r}^{2} \\ area \: = \: \: \pi \: \times {5}^{2} \\ area \: = \: \: \pi \: \times \: 25 .....(i)$

area increased to 4 times

hence , new area = 4 × 25 × \pi

new area = 100 × \pi

since, area = \pi × {r}^{2}

100 × \pi = \pi × {r}^{2}

100 = {r}^{2}

r = 10