Question

Janie inflated a ball to a radius of 18 cm and another ball to a radius of 12 cm. How much greater was the volume of air in the larger ball than the smaller ball?

Use 3.14 to approximate pi. Round to the nearest hundredth if necessary.

_______cm^3

Answer 1

Formula for volume of a sphere: V = (4/3)pi*r^3

18 cm radius: VR = (4/3)pi*(18 cm)^3
12 cm radius: Vr = (4/3)pi*(12 cm)^3

Calculate both, and then subtract the 2nd from the first. I would take the short cut of finding the difference as follows:

Difference in volume = (4/3)(3.14)*[18^3 - 12^3] cm^3