Find the weight help!!!!!!!

Question

A hollow iron pipe is 21 cm long and its external diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weighs 8 g/cm³, then the weight of the pipe is:

Answer 1

The iron pipe long is(l) = 21 cm

External radius(2r) = 8 ⇒ r = 4cm

Internal radius(r₁) = 4 -1 = 3cm

volume of iron = [22/7(r^2 - r₁^2)l]cm³

= [22/7(4^2 -3^2)(21)]cm³

= [22/7(7)(21)]cm³

= 462 cm³

Weight of iron =( volume of iron * iron weight)(cm³ *gm/cm³)

                          =(462 * 8) gm

                         = 3696 gm

Weight of iron is = 3.696 kg