# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.8 – Part 4

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Q-9 Twenty seven solid iron spheres, each of radius and surface area are melted to form a sphere with surface area. Find the

Radius of the new sphere,

Ratio of

Solution:

When the spheres are melted the volume of molten material remains the same.

Volume ofsolid sphere of radius , Volume of the new sphere of radius …………….equation (2), Since the volume must remain the same, therefore,

Required ratio of surface area,

=

or the ratio is

Q-10 A capsule of medicine is in the shape of a sphere of diameter. How much medicine (in) is needed to fill this capsule?

Solution:Diameter of the spherical capsule , Therefore, radius (r) , Medicine needed for filling this capsule = Volume of this spherical capsule