Question

The outer radius and the inner radius of a 30 cm long cylindrical gold pipe are 14 cm and 7 cm respectively. It is filled with bronze. The densities of gold and bronze are 20gm/`cm^(3)` and 30gm/`cm^(3)` respectively. Find the weight of the cylinder formed. (in gm)
A. `66150pi`
B. `99225pi`
C. `132300pi`
D. `198450pi`

Answer 1

Correct Answer - C
Volume of the pipe `=pi (14^(2)-7^(2))(30)cm^(3)`
` :. " Volume of the gold "=pi (14^(2)-7^(2))(30)cm^(3)`
Volume of the bronze in the pipe `=pi (7)^(2)(30) cm^(3)`
Weight of the pipe (in gms) = Weight of gold in it (in gm) + Weight of bronze in it (in gm)
`=[pi (14^(2)-7^(2))(30)][20]+[pi(7)^(2)(30)][30]`
`=30pi[(196-49)(20)+(49)(30)]`
`=30pi [2940 + 1470]=132300 pi gm.`