Question

The area of a circular ring between two concentric circles of radii r and (r + h) units respectively is given by

• A. $\pi (2r+h)hsq.units$
• B. $\pi (r+h)hsq.units$
• C. $\pi (r+2h)hsq.units$
• D. $\pi (r-h)hsq.units$

Answer 1

The correct option is A $\pi (2r+h)hsq.units$

Let us given $R=r+h$ $units$ & $r$ $units$ be the radii of outer and inner circle respectively.

Required area, $A=$ area of bigger circle - area of smaller circle

$=\pi (r+h{)}^2-\pi r^2$

$=\pi (r^2+h^2+2hr-r^2)$

$=\pi (h^2+2hr)$

$=\pi (h+2r)h$