A ratio compares two quantities. It can be written as a:b, a/b, or "a to b." Ratios can be simplified just like fractions by dividing both parts by their greatest common factor.

A proportion states that two ratios are equal. To solve a proportion like x/4 = 6/8, cross-multiply: 8x = 24, so x = 3. You can also think of it as scaling: 6/8 simplifies to 3/4, so x = 3.

A unit rate expresses a ratio with a denominator of 1. If you drive 150 miles in 3 hours, the unit rate is 150 ÷ 3 = 50 miles per hour. Unit rates make it easy to compare options.