Question

The area is enclosed bw the concentric circles is 770cm2,if the radius of the outer circle is 21cm,calculate the radius of the inner circle.

Answer 1

Answer:

given area =770

radius (R)=21 cm

Step-by-step explanation:

$\pi  R^2 -\pi r^2=770\\\pi (R^2-r^2)=770\\21^2-r^2=770\pi \\ (taking \pi as 22/7)\\441-r^2=245\\-r^2=-196\\r=13$