The diameter of the Moon is approximately one-fourth of the diameter of the Earth. What is the ratio (approximate) of their volumes?

Given that, the diameter of moon is approximately one-fourth of the diameter of Earth.
Let radius on moon = r
Then, radius of Earth = 4r
∴ Volume of Moon/Volume of Earth
= [(4/3)πr³] / [(4/3)π(4r)³]
= [r³] / [64r³] = 1/64 = 1 : 64