Estimation question

How many balls does it take to fill a 16x16 ft room?

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Spatial estimation: decomposing a volume problem into simple geometric assumptions.

Calculate room volume: assume an 8 foot ceiling, so 16 times 16 times 8 gives roughly 2,048 cubic feet.
Assume a standard ball size, such as a beach ball or a ball pit ball around 3 inches (0.25 feet) in diameter.
Calculate single ball volume using the sphere formula, roughly 0.008 cubic feet per 3 inch ball.
Account for packing efficiency, since spheres do not fill space perfectly, assume roughly 60 percent packing density.
Divide usable volume (2,048 times 0.6) by ball volume to estimate total balls, landing in the low millions.
Present the final number as a rounded estimate and state the ball size assumption clearly, since it drives the whole answer.

States the ball size assumption explicitly up front, since the answer changes by orders of magnitude depending on this choice.
Applies a packing efficiency factor rather than assuming perfect space filling, which shows geometric awareness.
Shows clean step by step arithmetic so the interviewer can follow and adjust any assumption.
Gives a final rounded range instead of a falsely precise single number.

Skipping the packing efficiency factor and assuming balls fill 100 percent of the volume.
Not stating an assumed ball size, making the final number meaningless.
Giving an implausibly precise final answer with no rounding.

Chapters of the AI PM course that teach what this question tests.