Question

a hollow cylinder tube open at both end is made of iron 3cm thick if the external diameter be 56cm and the lenth of tube be 182cm find the number of cubic cm in it

Answer 1

Given, thickness of iron =3cm
          external diameter = 56cm
               Length of tube = 182cm
We know,
  volume of hollow cylinder = πh(R²−r²)
∴ internal diameter = external diameter−2×thickness of iron
                               = 56−2×3
                               = 56−6
                               = 50cm

=> Outer radius(R) = 56÷2 = 28cm
       inner radius(r) = 50÷2 = 25cm
∴ Volume of hollow cylinder = πh(R²−r²)
3.14×182(28²−25²)
                                        = 3.14×82×159
                                        = 90865.32cm³       Answer

please see the attachment for diagram of cylinder mentioned in the question