Question

The circumference of two concentric circles are $121$cm and $154$ cm. calculate the difference between their radii.

Answer 1

REF.image

Given circumference of circle A= 121 cm.

Given circumference of circle B= 154 cm.

now $r_1$ be radius of circle A & $r_2$ be radius of circle B.

now $2\pi r_1=121$

$r_1=\frac{121}{2\pi }$ ...(1)

and $2\pi r_2=154$

$r_2=\frac{154}{2\pi }$ ...(2)

now $r_2-r_1=\frac{154}{2\pi }-\frac{121}{2\pi }=\frac{1}{2\pi }[154-121]$

$r_2-r_1=\frac{33}{2\pi }=5.25$