Answer:
a) Given radius, r = 21 cm
Circumference of the circle, C = 2πr
= 2 × 3.14 × 21 cm
= 131.88 cm
Area of the circle, A = πr^2
= 3.14 × 21^2 cm^2
= 1385.94 cm^2
b) Given diameter, d = 70 mm
Radius of the circle, r = d/2
= 35 mm (1 cm = 10 mm)
Circumference of the circle, C = 2πr
= 2 × 3.14 × 35 mm
= 219.8 mm
Area of the circle, A = πr^2
= 3.14 × 35^2 mm^2
= 3847.5 mm^2
c) Given radius, r = 4.9 m
Circumference of the circle, C = 2πr
= 2 × 3.14 × 4.9 m
= 30.73 m
Area of the circle, A = πr^2
= 3.14 × 4.9^2 m^2
= 75.36 m^2