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Home » A metallic disc, in the shape of a right circular cylinder, is of height 2.5 mm and base radius 12 cm. Metallic disc is melted and made into a sphere. Calculate the radius of the sphere.
A metallic disc, in the shape of a right circular cylinder, is of height 2.5 mm and base radius 12 cm. Metallic disc is melted and made into a sphere. Calculate the radius of the sphere.
CBSE | Class 10 | Exercise 1 | maths | Maths | Mensuration | ML Aggarwal
A metallic disc, in the shape of a right circular cylinder, is of height 2.5 mm and base radius 12 cm. Metallic disc is melted and made into a sphere. Calculate the radius of the sphere.

Solution:

Given height of the cylinder, h = 2.5 mm = 0.25 cm

Radius of the cylinder, r = 12 cm

Volume of the cylinder = r2h

= ×122×0.25

= ×144×0.25

= 36 cm3

Let R be the radius of the sphere.

Volume of sphere = (4/3)R3

Since metallic disc is melted and made into a sphere, their volumes remains same.

(4/3)R3 = 36

R3 = 36×3/4

R3 = 27

Taking cube root

R = 3 cm

Hence the radius of the sphere is 3 cm.

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