Kilometers made easy.

I recently came across this page with someĀ  formulas for converting miles to kilometers. There is one that’s simple enough to do in your head:

Divide the number of miles by five and subtract that from the original. Then double the resulting number.

So I started by converting some of the speed limits from around town:

mph km/h
40 64
45 72
65 104
70 112

That’s when I noticed something interesting. When you add 5 to the miles per hour being converted, its metric equivalent goes up by 8. In other words, whenever a speed in miles per hour is a multiple of 5, its corresponding kilometers per hour will be a multiple of 8. Mind blowing or what. It’s then that a pattern begins to form and all of a sudden, understanding kilometers becomes less intimidating.

mph km/h
5 8
10 16
15 24
20 32
25 40
30 48
35 56
40 64
45 72
50 80

And so the pattern continues towards an easier way to understand the metric system.