The perimeter of a sector of a circle of radius 21cm is 64cm. Find the angle of the sector [Take \(\pi = \frac{22}{7}\)]

A.

70o

B.

60o

C.

55o

D.

42o

Correct answer is B

Perimeter of a sector

= 2r + \(\frac{\theta}{360^o}\) x 2 x \(\frac{22}{7}\) x 21

64 = 2 x 21 + \(\frac{\theta}{360^o}\) x 2 x \(\frac{22}{7}\) x 21

64 = 42 + \(\frac{\theta}{360^o}\) x 44 x 3

64 - 42 = \(\frac{\theta}{360^o}\) x 11 x 3

22 = \(\frac{33\theta}{90}\)

\(\theta = \frac{22 \times 30}{11}\)

= 60o