Converting: English Style

Last time I talked about converting between metric units. This was pretty easy for me (even using powers of 10).

Although this time, I’ll be talking about converting between English units. My friend showed me this little trick on remembering the conversion rate between gallons and cups. It’s called the Gallon Man.

Ain’t it cute!

Anyway, the reason that conversions between English units are harder is because the conversion factors are not standardized and are very random. So, converting between English units takes a longer process than just multiplying and dividing by 10. The easiest way to convert is cross cancellation of units.

Ex)  1m│100cm = 100cm

        1   │ 1m            1

m → cm

The two m (meter) are cancelled out because m/m=1.

Let’s try one a little more complicated

Ex) 200cm│   1m     │  1km  │ 60sec │60min =  720,000km = 72km =   72km/hr

         1sec │ 100cm │ 100m│ 1 min   │1 hr          10,000 hr       1hr

This conversion shows cm/sec → km/hr

Cross cancellation works by multiplying all the top numbers together then dividing it by the product of all the bottom numbers.