Direct variation: 2 variables related directly with a constant of proportionality (i.e. y/x=k or y=2k)
Inverse variation: 2 variables related inversely with a constant of proportionality (i.e. yx=k or y=k/x)
Constant of proportionality: a fixed number representing the ratio between y and x
A little visual help with direct variation
More visual help, this time on inverse variation
