3QUESTION 3 OF 3
Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
80,000,000
people
How to estimate it
Fermi’s official “Napkin math”
The easiest place to start is the world's population, about 8 billion. How many of them need a wheelchair to get around? Not a huge share, maybe 1 in 100.
- World population
- 8,000,000,000
- Need a wheelchair
- ≈ 1 in 100
- 8B ÷ 100
- ≈ 80 million
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- WHO wheelchair provision guidelines (2023)
- 80 million people, about 1% of the world's population, are likely to require a wheelchair
- Rounded
- ≈ 80 million
Reference cited by Fermi: World Health Organization wheelchair provision guidelines
How close was your guess?
Your comparison will appear here.
Compare by ratio: divide the larger number by the smaller one. The closer to 1×, the better.