Question

a hollow cylindrical pipe is 21 m long. It's inner and outer diameter are 16 cm and 10 cm respectively.find the volume of the metal used in making the pipe.

Answer 1

Inner diameter=10 cm
Inner radius=D/2=(10/2)=5cm
Height=21m=2100cm
inner volume =pi*r*r*h
Outer diameter=16cm
Outer radius=D/2=(16/2)=8cm
Outer volume=pi*R*R*h
Volume of metal=Outer volume-Inner volume
pi*R*R*h-pi*r*r*h
22/7*8*8*2100-22/7*5*5*2100
422400-165000
257400cu.cm
therefore,257400cu.cm of metal is used