Question

.A 20m long iron pipe has an exterior diameter equal to 25cm. If the thickness of the pipe is 1 cm. Find the whole surface of the pipe

Answer 1

Length of the pipe = 20 cm
External diameter = 25 cm
External radius, R = 12.5 cm
Thickness of the pipe, w = 1 cm
Internal radius = 12.5 – 1 = 11.5 cm
Area of the pipe = outer area – inner area
Outer area = 2πr(r + h)
= 2π×12.5(12.5 + 20) = (812.5)π
Inner area = 2π×112.5(11.5 + 20) = (724.5)π
Hence area of the pipe = (812.5)π – (724.5)π = 88π