If the ratio of the volumes of the two sphere is 125 : 64, find the ratio of their surface areas.
Solution:
The amount of space that a sphere can occupy is measured by its volume. If we take a circular disc, attach a string to its circumference, then rotate it along the string, we can create a circle on a piece of paper. This provides us a sphere-like form.
Given ratio of volume of two spheres = 125/64
(4/3)π r13/(4/3)π r23 = 125/64
r13/ r23 = 125/64
Taking cube root on both sides
r1/r2 = 5/4
Ratio of surface areas of the spheres =
4π r12/4π r22
= r12/r22
= 52/42
= 25/16
Hence the ratio of the surface areas is 25:16.
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