Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
75
minutes
How to estimate it
Fermi’s official “Napkin math”
Alcatraz sits about a mile off the San Francisco shore. How fast does a goldfish actually swim? Slowly, maybe 1 mile an hour. So it works out to roughly an hour of paddling.
- Distance to shore
- ~1 mile
- Goldfish speed
- ~1 mph
- 1 mile ÷ 1 mph
- ≈ 1 hour
Alcatraz sits about 2 kilometers off the San Francisco shore. How fast does a goldfish actually swim? Slowly, maybe 2 kilometers an hour. So it works out to roughly an hour of paddling.
- Distance to shore
- ~2 km
- Goldfish speed
- ~2 km/h
- 2 ÷ 2
- ≈ 1 hour
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Alcatraz to SF shore
- ~1.25 miles
- Goldfish cruising speed
- ~1 mph
- 1.25 mi ÷ 1 mph
- ≈ 75 min
Reference cited by Fermi: NPS Alcatraz / goldfish swim speed estimates
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.