Question

If the radii of two concentric circles are 15 cm and 13 cm, respectively, then the area of the circulating ring in sq. cm is ___.

• A. 176 sq.cm
• B. 178 sq.cm
• C. 180 sq.cm
• D. 200 sq.cm

Answer 1

The correct option is A 176 sq.cm

R =15 cm, r =13 cm.
Where R is radius of the larger circle and r is radius of the smaller circle
Area of the circulating ring =$\pi (R^2-r^2)$
$=\pi (R+r)(R-r)=\frac{22}{7}(15+13)\times (15-13)=\frac{22}{7}\times 28\times 2=176sq.cm$