Using π = 22/7, find the perimeter of the semi-circle whose diameter is 21cm long.

Correct option is C

Given:

​$$π = \frac{22}{7}$$​​

semi-circle diameter = 21 cm .

Formula used:

Perimeter of semi-circle =  πr + d

r     is the radius of the semi-circle.

d   is the diameter of the semi-circle. 

Solution:

Diameter d = 21cm,

So, the radius r = $$\frac{d}{2}$$ = $$\frac{21}{2}$$= 10.5cm

​Perimeter= π × r + d 

= $$\frac{22}{7}$$ $$\times$$ 10.5 + 21

$$= \frac{22\times 10.5}{7}+21$$

$$=\frac{231}{7}+21$$

= 33+21

= 54cm

The perimeter of the semi-circle is 54 cm.

Thus, correct option is (c)