Multiple choice

Three spheres of radii 3 cm, 4 cm and 5 cm are melted to form a new sphere. The radius of the new sphere is -

  1. 6 cm

  2. 7.5 cm

  3. 10 cm

  4. 12 cm

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When spheres are melted and recast, volume is conserved. Volume of a sphere = (4/3)πr³. Total volume = (4/3)π(3³ + 4³ + 5³) = (4/3)π(27 + 64 + 125) = (4/3)π(216). For the new sphere: (4/3)πR³ = (4/3)π(216), so R³ = 216, giving R = 6 cm.