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

For spherical objects, such as these planets, the volume is calculated by the equation,

V = 4πr³ / 3

where V is volume and r is the radius. To determine the number of Plutos that would fit in the Earth, divide the volume of Earth by the volume of Pluto.

V (E) / V (P) = (4π (6371 km) ³ / 3) / (4π (1161 km) ³ / 3)

= 165.2

Thus, the answer is approximately 165.