Estimation question

How many cars are on 101 between San Francisco and Mountain View?

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

Fermi estimation using distance, lane count and traffic density.

Estimate the distance between the two points, roughly 35 miles.
Assume the number of lanes each direction, e.g. 4.
Assume average car spacing during a given time of day, e.g. one car every 100 feet per lane in moderate traffic.
Convert spacing to cars per mile per lane, then multiply by lanes and distance.
State assumptions clearly and give a range depending on time of day.
Sanity-check the final number's order of magnitude.

Anchors on real distance rather than guessing the segment length.
States the car-spacing assumption explicitly and converts it cleanly to cars per lane-mile.
Distinguishes rush-hour density from off-peak, since the answer varies by an order of magnitude.
Shows the full multiplication chain rather than asserting a final number.

Not accounting for time-of-day variation, which massively changes traffic density.
Skipping the distance or lane-count assumption, leaving the math unclear.

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