NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.8 – Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for CBSE/Class-9 : get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-9.

Volume of Sphere = 4/3 Πr ^ 3

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

  1. Radius of the new sphere,
  2. Ratio of

Solution:

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

  1. Volume of solid sphere of radius , Volume of the new sphere of radius … equation (2) , Since the volume must remain the same, therefore,
  2. Required ratio of surface area,
  3. =
  4. 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

Developed by: