4 ms·
There's a slightly quicker way that they kind of stumble upon, but never outright say. miles * 8/5 = km and km * 5/8 = miles. How many km in 100 miles? 100/5 =
by bena 2y ago
There's a slightly quicker way that they kind of stumble upon, but never outright say. miles * 8/5 = km and km * 5/8 = miles.
How many km in 100 miles? 100/5 = 20, 20 * 8 = 160.
How many miles in 400km? 400/8 = 50, 50 * 5 = 250.
And 8/5 is 1.6 exactly, which is close to the "golden ratio".
- j0057 2y agoWhen driving in the UK, I found myself practicing my 16-table a lot: when seeing a 50 mph max speed sign, I'd multiply 5 by 16 to get 80 km/h.
- robertlagrant 2y agoHah I've just been driving in France and kept multiplying by 0.6. Much simpler than 16!
- NikkiA 2y agoGiven (official*) UK speed limits are always in multiples of 5, using the 8/5 rule would be quicker and work just as well. * There are occasional places where private property has speed limits with weird factors, but they're so rare as not to worry about. (the one example I remember is when I used to cycle to work and took shortcuts through a sewage plant that had an '11 mph' speed limit, why? who knows.
- gjm11 2y agoIf you want real accuracy, note that the actual mile/km ratio is almost exactly half way between 1.6 and (1+sqrt(5))/2. So do both conversions and take the average. (You won't get results as accurate as that suggests, of course, because doing the Zeckendorff + Fibonacci-shift thing only gives you an approximation to multiplying by (1+sqrt(5))/2.)