Math basics › Numbers and fractions
Ratios and proportions
A proportion is two equal ratios
a/b = c/d. Cross-multiply to get ad = bc, then solve.
Keep the units in the same place
If miles are on top on the left, miles go on top on the right. Most proportion errors are a flipped ratio.
Unit rate
Divide until the bottom is 1. It makes two offers comparable, and it is the same idea as slope.