Product Sense · medium · Asked at Lyft

Estimate the number of ride requests in a city per day.

Asked in Data Analyst interviews.

Short answer

Market sizing: population x adoption x trips/day; state assumptions clearly.

How to answer it

The interviewer wants a structure and stated assumptions, not the right number. Say the structure first, then fill it in.

Requests per day equals people who might ride, times the share who use ride-hailing, times rides per user per day, adjusted for cancellations and multi-request behaviour.

Worked example for a city of 5 million:

• Adults with a smartphone and access: about 70%, so 3.5 million.
• Share who use ride-hailing at all in a given month: say 25%, so about 900,000 monthly users.
• Rides per monthly user: heavy users daily, most a few times a month; a blended 4 per month is plausible, giving 3.6 million rides a month, about 120,000 a day.
• Requests exceed completed rides: cancellations, re-requests, no-driver events. Add 20%, so roughly 150,000 requests a day.

Then sanity-check against something you know: 150,000 requests across a fleet of, say, 20,000 active drivers is 7 to 8 requests per driver per day, which is a believable shift. If the number came out at 100 per driver, an assumption is wrong.

Say which assumption the answer is most sensitive to (the monthly usage share) and how you would pin it down with data (app installs, or a survey, or the company's own numbers for a comparable city).

• What they are checking: a clean decomposition, explicit assumptions, and a sanity check at the end.
• Common mistake: precision theatre. Quoting 147,320 from assumptions that are each plus or minus 50%.

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