Convert miles and kilometres in your head
5 miles is about 8 km. That one pair, plus a bit of Fibonacci, covers every road sign abroad.
- Remember 5 miles ≈ 8 km.
- Miles to km: multiply by 8, divide by 5. 50 miles → 400 ÷ 5 = 80 km.
- Km to miles: multiply by 5, divide by 8. 40 km → 200 ÷ 8 = 25 miles.
- Or use neighbouring Fibonacci numbers: 3 → 5, 5 → 8, 8 → 13, 13 → 21 (miles → km).
Tip: A mile is exactly 1.609344 km, so these are close but slightly rough; fine for signs and runs, not for engineering.
Try it now: How far is a 10 km run in miles, and what's 30 mph in km/h? [About 6.2 miles, and about 48 km/h.]
Next crumbs
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