The volumes of a sphere and a right circular cylinder (with the same radius) are equal. Find the ratio of the diameter of the sphere to the height of the cylinder.

Difficulty: Easy

Correct Answer: 3 : 2

Explanation:


Introduction / Context:
Equate volumes of sphere and cylinder with common radius r. Express the cylinder height in terms of r, then form the ratio of sphere diameter to that height.


Given Data / Assumptions:

  • V_sphere = (4/3)πr^3.
  • V_cyl = πr^2h.
  • Equal volumes: V_sphere = V_cyl.


Concept / Approach:
Solve (4/3)πr^3 = πr^2h for h, then compute (diameter):(height).


Step-by-Step Solution:

(4/3)πr^3 = πr^2h ⇒ h = (4/3)rDiameter of sphere = 2rRatio = 2r : (4/3)r = 2 : 4/3 = 3 : 2


Verification / Alternative check:
Cancel π and r^2 safely since r > 0; ratio reduces cleanly.


Why Other Options Are Wrong:
They do not reflect h = 4r/3 and D = 2r.


Common Pitfalls:
Using circumference or surface areas instead of volumes; forgetting diameter is 2r.


Final Answer:
3 : 2

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