1QUESTION 1 OF 3
Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
20,000
pens
How to estimate it
Fermi’s official “Napkin math”
The way round the Earth is about 40,000 kilometres. How long a line does one pen draw before it gives up? Further than you would think, a couple of kilometres.
- Around the Earth
- 40,000 km
- One pen writes
- ÷ 2 km
- 40,000 ÷ 2
- ≈ 20,000
The way round the Earth is about 25,000 miles. How long a line does one pen draw before it gives up? Further than you would think, call it a mile.
- Around the Earth
- 25,000 mi
- One pen writes
- ÷ 1 mi
- 25,000 ÷ 1
- ≈ 25,000
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Earth's equatorial circumference
- = 40,075 km
- Line one BIC Cristal writes (BIC's own claim)
- = 2 km
- 40,075 ÷ 2
- ≈ 20,000 pens
Reference cited by Fermi: BIC Cristal product claim
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.