A cylindrical tube open at both ends has been made of iron sheet which is 2cm thick. If the outer diameter is 16 cm and its length is 100 cm, find how many cubic centimeters of iron has been used in making the tube.

Outer dia=16
Outer radius= 8cm= R_outer

Inner radius= Outer radius – thickness of tube= 8-2= 6 cm

So, Volume of iron used= pi*h*(R²_outer-R²_inner)= Volume of outer cylinder- volume of inner cylinder

D_o=16cm
thickness t = 2 cm
So Inner dia D_i=16-4 = 12cm
Length = 100cm

So outer radius R_o=8cm
So inner radius R_i=6cm

So volume of tube = R_o²h – R_i²h
Now put all the values