It's nice to have some quick mental conversions ready.
1 mile is roughly 1.6 km, so 100 miles is roughly 160 km
3 feet is roughly a meter
2 pounds are roughly 1 kg
1 gallon is roughly 4 liters
32 fahrenheit it 0 celcius, 100 fahrenheit is slightly over body temperature, 200 fahrenheit is almost enough to boil water... Any other value requires math to figure out...