The radii of earth and pluto are 6,371 kilometers and 1,161 kilometers, respectively. approximately how many spheres the size of pluto does it take to have the same volume as earth?
121
154
165
176
189

The volume of a sphere is

                       (4/3 π) x (radius)³ .

Right there, we can see that the volume of a sphere is proportional to
the cube of its radius, and the ratio of the volumes of two spheres is
the same as the cube of the ratio of their radii.

The ratio of the radii is                (6,371 / 1,161)  =  5.4875... (rounded) .

So the ratio of their volumes is     (6,371 / 1,161)³  =  (5.4875)³ = 165.24 .

Words cannot express our boundless joy when we look up
at the list of choices and see that  165  is one of them.

The volume of Earth: VE=4/3 · 6371³ π 
The volume of Pluto:  VP=4/3 · 1161³ π
(4/3 · 6371³ π ) : (4/3 1161³ π )= ( 5.48751 · 1161 )³ : 1161³ = 5.48751³=
=165.24
C) 165