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Estimationstretch
How much would it cost to repaint every yellow school bus in the US?
How to approach it
Estimate the number of buses first, then cost per bus from paint, labor and time off the road.
How a strong answer opens
“I'll estimate the number of school buses first, from students who ride and students per bus, then cost per bus for paint, labor and time out of service.”
Outline of a strong answer
Try answering out loud for a few minutes before you open this.
- Estimate school buses from students who ride
- Students per bus
- Paint and labor cost per bus
- Optional: cost of buses being out of service during the school year
- Multiply buses by cost per bus
- Sanity-check: compare the total to the cost of buying new buses
Where this question usually goes wrong
Guessing the bus count with no derivation, or forgetting labor and time off the road, which cost more than the paint.
Learn the method
Top-down and bottom-up in Module 3, Estimation.
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