3QUESTION 3 OF 3
Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
10,000
PIN codes
How to estimate it
Fermi’s official “Napkin math”
Each of the four digits can be anything from 0 to 9, so 10 choices each. How do they combine? Every first digit can go with every second digit, and so on, so you multiply.
- Choices per digit
- 10
- Four digits
- × 10 × 10 × 10
- 10 × 10 × 10 × 10
- = 10,000
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Choices for each digit, 0 to 9
- 10
- Four digits
- 10 × 10 × 10 × 10
- Every code from 0000 to 9999
- = 10,000
Reference cited by Fermi: DataGenetics PIN number analysis (Nick Berry, 2012): 10,000 possible codes, 0000 to 9999
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.