Question

# An iron spherical ball of radius 21 cm is melted and it is re-cast into small hemispheres radius 7 cm each. The number of hemispheres formed will be54 52 48 50

Solution

## The correct option is A 54 Given, Radius of the spherical ball,R=21 cm Radius of each hemispherical ball,r=7 cm The volume will remain constant as same volume of iron metal is used to re-cast the hemispherical balls. Let's assume x such hemispherical balls will be formed. So, Volume of spherical ball = x × Volume of each hemispheical ball  ⇒43πR3=x×23πr3 ⇒43×π×213=x×23×π×73 ⇒x=54 ∴ After re-casting 54 small hemispherical balls are formed.

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