Volume of a Sphere Math Example 4

Follow the full solution, then compare it with the other examples linked below.

Example 4

hard
If the radius of a sphere is doubled, by what factor does its volume increase? Prove your answer algebraically.

Solution

  1. 1
    Step 1: Original volume with radius rr: V1=43ฯ€r3V_1 = \frac{4}{3}\pi r^3.
  2. 2
    Step 2: New volume with radius 2r2r: V2=43ฯ€(2r)3=43ฯ€ร—8r3=8ร—43ฯ€r3V_2 = \frac{4}{3}\pi (2r)^3 = \frac{4}{3}\pi \times 8r^3 = 8 \times \frac{4}{3}\pi r^3.
  3. 3
    Step 3: Find the ratio: V2V1=8ร—43ฯ€r343ฯ€r3=8\frac{V_2}{V_1} = \frac{8 \times \frac{4}{3}\pi r^3}{\frac{4}{3}\pi r^3} = 8.

Answer

The volume increases by a factor of 88.
Since volume scales as the cube of the linear dimension (Vโˆr3V \propto r^3), doubling the radius multiplies the volume by 23=82^3 = 8. This is a fundamental principle: if all linear dimensions scale by factor kk, volumes scale by k3k^3. It applies to any 3D shape, not just spheres.

About Volume of a Sphere

The amount of three-dimensional space inside a sphere, given by 43ฯ€r3\frac{4}{3}\pi r^3.

Learn more about Volume of a Sphere โ†’

More Volume of a Sphere Examples