Question

A metallic pipe whose internal and external diameters are 8 cm and 6cm has a length of 2.1 metre. Find the volume of the metal.

Answer 1

Solution:-
The external diameter of the pipe = 8 cm
The internal diameter of the pipe = 6 cm 
External radius = 4 cm and it is denoted as 'R'
Internal diameter = 3 cm and it is denoted as 'r'
Length or height of the pipe = 2.1 m or 210 cm
Volume of the metal = Outer volume of pipe - Inner volume of pipe
= πR²h - πr²h
= (22/7*4²*210) - (22/7*3²*210)
10560 - 5940
Volume of the metal = 4620 cm³
Answer.

Answer 2

External diameter = D = 8
External radius = R = 8/2 = 4
Internal diameter= d = 6
Internal radius = r = 6/2 = 3
length of pipe= h = 2.1m or 210 cm

Volume of metal = Outer volume - inner volume
= λ (R +r) (R-r) h
= 22/7 (4 +3) (4-3) 210
= 4620