Convert 80 kilometres to miles

Question

Solve in your head. What is 80 km in miles? Aim: under 10 seconds.

Accepted Answer

One kilometre is about 0.621 miles, so 80 	imes 0.621 \approx 80 	imes 0.6 + 80 	imes 0.021 = 48 + 1.7 \approx 49.7 	ext{ miles.} Call it \approx 50 miles. A neat cross-check: consecutive Fibonacci numbers approximate the km-to-mile ratio. Since 8 km \approx 5 miles, 80 km \approx 50 miles. Takeaway. Use 	imes 0.62 for km	omi and 	imes 1.61 for mi	okm. The Fibonacci trick (5	ext{–}8, 8	ext{–}13, 13	ext{–}21) is a charming shortcut because the golden ratio 1.618 sits astonishingly close to the true factor 1.609.

Convert 80 kilometres to miles

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