Question

find the circumference of a circle whose (1) radius=21cm (2) diameter=63cm?

Answer 1

1. r = 21 cm
C = 2πr
= 2 × 22/7 × 21
= 2 × 22 × 3
= 132 cm

2. d = 63
so, r = 63 / 2 = 31.5

C = 2πr
= 2 × 22/7 × 31.5
= 198 cm

Answer 2

1) radius= 21cm
Circumference of circle=2× 22/7× 21
= 132cm

2) diameter= 63cm
radius= 63/ 2
= 31.5cm
Circumference of circle= 2× 22/7× 31.5
= 198cm