Question

Calculate the area and perimeter of a ring where the outer circle has a radius of 21 cm and inner circle has radius of 14cm

Answer 1

Step-by-step explanation:

Outer radius,R = 21cm

Inner radius,r = 14cm

Ar. of outer circle = πR² = 22/7×21²

= 1386 cm²

Ar. of inner circle = πr² = 22/7×14² = 616cm²

Ar.of ring = ar. of outer circle - ar. of inner circle = (1386-616)cm² = 770cm²

Perimeter of outer circle = 2πR = 2×22/7×21

= 132 cm

Perimeter of inner circle = 2πr = 2×22/7×14

= 88 cm

Perimeter of ring = perimeter of outer circle + perimeter of inner circle = (132+88)cm

= 220 cm