(a) It is given in the question that,

Radius of the circle = 14 cm

We know that,

Circumference of the circle = 2πr

= 2 × π × 14

= 2 × (22/7) × 14

= 2 × (22/7) × 2

= 88 cm

(b) It is given in the question that,

Radius of the circle = 28 mm

We know that,

Circumference of the circle = 2πr

= 2 × π × 28mm

= 2 × (22/7) × 28mm

= 2 × (22) × 4

=176 mm

(c) It is given in the question that,

Radius of the circle = 21 cm

We know that,

Circumference of the circle = 2πr

= 2 × π × 21 cm

= 2 × (22/7) × 21 cm

= 2 × (22) × 3 cm

= 132 cm