1.

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 densitiesof gold and bronze are 20gm/cm^(3) and 30gm/cm^(3) respectively. Find the weight of the cylinder formed. (in gm)

Answer»

`66150pi`
`99225pi`
`132300pi`
`198450pi`

Solution :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) + WEIGHTOF 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.`


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