The external diameter of an iron pipe is 20 cm and its length is 12 cm. If the thickness of the pipe is 1 cm, find the surface area of the pipe (take π = 22/7) correct to two places of decimal.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 1,552.57 cm2.
The external diameter of an iron pipe = 20 cm
R = 20/2 = 10
length = 12 cm
Thickness = 1 cm
So, the inner radius r = 10 - 1 = 9 cm
TSA of hollow pipe = 2πh(R + r) + 2π (R2-r2)
= 2π × 12(10 + 9) + 2π(10 + 9)(10 - 9)
= 456π + 38π
= 494 × 3.14
= 1,552.57 cm2