A proportional relationship shows that two things change at the same rate.
If you double one, you double the other — the ratio stays the same.
If 3 apples cost 6 dollars,
then 6 apples cost 12 dollars — because 3:6 = 6:12
Both ratios simplify to one-half.
Proportional thinking is used in recipes, scale drawings, maps, money, and unit pricing.