A direct proportion means the ratio of p:u is a constant number
This constant number is denoted by k
an example of this is, say for every 1 chicken you buy there are 2 legs which is ratio 1:2 which is [tex]\frac{1}{2}[/tex]
so if you add more chickens, you add more legs, 2 chickens means 4 legs, 8 chickens means 16 legs, which is [tex]\frac{1}{2}= \frac{2}{4} =\frac{8}{16} =0.5[/tex] so the constant number is 0.5, so this a direct proportion
