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  1. A copper rod of diameter 1 cm. and length 8 cm. is drawn into a wire of length 18m of uniform thickness. Find the thickness of the wire.

  2. Pravali’s house has a water tank in the shape of a cylinder on the roof. This is filled by pumping water from a sump (an under ground tank) which is in the shape of a cubiod. The sump has dimensions 1.57 m. ́ 1.44 m. ́ 1.5 m. The water tank has radius 60 cm. and height95cm. Find the height of the water left in the sump after the water tank has been completely filled with water from the sump which had been full of water. Compare the Capacity of the tank with that of the sump.


Example-15.The diameter of the internal and external surfaces of a hollow hemispherical shell are 6 cm. and 10 cm. respectively. It is melted and recast into a solid cylinder of diameter 14 cm.Find the height of the cylinder.

Solution : Outer radius of hollow hemispherical shell R=10/2=5cm

Internal radius of hollow hemispherical shell (r) = 6/2 = 3cm

Volume of hollow hemispherical shell

= External volume - Internal volume

Since, this hollow hemispherical shell is melted and recast into a solid cylinder. So their volumes must be equal

Diameter of cylinder = 14 cm. (Given)

So, radius of cylinder = 7 cm.







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