Question

If the diameters of two concentric circles are 20 cm and 16 cm then the area of the circular ring included between the two circles is​

Answer 1

$\underline{\textbf{Given:}}$

$\textsf{Diameters of two concentric circles are 20 cm and 16 cm}$

$\underline{\textbf{To find:}}$

Area of the circular ring included between

the given two concentric circles

$\underline{\textbf{Solution:}}$

$\mathsf{Let\;r_1\;and\;r_2\;be\;radii\;of\;given\;concentric\;circles\;with\;r_1>r_2}$

$\textsf{As per given data,}$

$\mathsf{2\;r_1=20\;cm\;\;\&\;\;\,r_2=16\;cm}$

$\mathsf{r_1=10\;cm\;\;\&\;\;\,r_2=8\;cm}$

$\mathsf{Now,}$

$\textsf{Area of the circular ring}$

$\mathsf{=\pi\,{r_1}^2-\pi\,{r_2}^2}$

$\mathsf{=\pi({r_1}^2-{r_2}^2)}$

$\mathsf{=\pi(10^2-8^2)}$

$\mathsf{=\pi(100-64)}$

$\mathsf{=36\,\pi\;cm^2}$

$\therefore\textbf{Area of the circular ring is}\;\mathsf{36\,\pi\,cm^2}$

$\underline{\textbf{Answer:}}$

$\textbf{Option (D) is correct}$