#unit conversion

Imagine your OTP. Person A is from America, and Person B is from another country. While driving around in the US, A keeps saying the wrong numbers when reading speed limit signs, much to B's confusion.

A: "Seventy-two."

B: "The sign says forty-five, A."

A: "Yeah, seventy-two."

B: "What the- can you not read? It clearly says-"

A: "Well, I thought you'd be more comfortable with kilometers per hour…"

B: "...what."

*pause*

B: "How are you doing that in your head, you say it right after seeing the sign."

A: "It's a simple ratio. Five-to-eight."

An example ACT Math Test question.

Try it for yourself first, then “keep reading” for the answer:

For any unit conversions, you can just make a ‘railroad’ with all of the individual unit equalities and multiply them out, remembering that these are really just fractions. You can flip conversions as long as the amount of the unit on top is still equal to the amount of the unit on the bottom.

I learnt it from engineering classes and it makes unit conversion much easier than multiplying individual conversions

(The units in the middle example are Swiss franks, great British pounds, and United States Dollars)