10th Class Mathematics Areas Related to Circles Question Bank MCQs - Areas Related to Circles

The circumferences of two concentric circles forming a ring are \[\text{88 cm}\] and 66 respectively. The width of the ring is:

A) \[14\,cm\]

B) \[7\,cm\]

C) \[\frac{7}{2}\,cm\]

D) \[21\,cm\]

Correct Answer: C

Solution :

[c] Let radius of outer circle = R cm

and inner circle =r cm

\[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,2\pi R-2\pi r=88-66=22\]

\[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,R-r=\frac{22}{2\pi }=\frac{7}{2}\,cm\]