Lifehacks

Yes. That uses the 3:5 ratio.

or add half and then 10% (because it’s 1.6km to the mile): easier than multiplying decimals or large numbers by 6, and the inverse is 0.6mi=1km so easy to remember both ways (same thing but don’t “add” just start from 0)

Honestly divide by 5 and multiply by 8 usually isn't too difficult and just gives you the right answer.

I remember it by 200mph is 320kph.

I used to remember because space (Karman line) is 100km or 62mi up. I guess it helps to be a space nerd for that one. Kind of just figure 1.6 going the other way.

Thank you, will definitely use this now on

glad I did not learn conversion in school. Nobody uses miles where i live