Question 39
Mensuration of SolidsA solid sphere of radius 4cm has a mass of 64kg. What will be the mass of a shell of the same metal whose internal and external radii are 2cm and 3cm respectively?
- A.5kg
- B.16kg
- C.19kg
- D.25kg
- E.48kg.
Show the answer and explanation
Answer: C (19kg)
Explanation
Mass ∝ r³. The shell's volume is proportional to 3³ − 2³ = 19 and the solid sphere's to 4³ = 64, so the mass is 64 × 19/64 = 19kg.