Which statement about unit rates is true?

• A. They compare two quantities with the same unit
• B. They require decimal forms in all cases
• C. They always have a numerator of 1
• D. They express how many units of one quantity per one unit of another quantity

Answer: (D)

Unit rates tell you how many units of one quantity you get for each one unit of another quantity. This makes it easy to compare things like speed or cost, because you’re looking at a per-one-unit measure.

For example, if you drive 60 miles in 2 hours, the unit rate is 30 miles per hour, since you’re measuring how many miles occur in one hour. The key idea is that you’re not restricting the two quantities to have the same unit; you’re expressing a quantity per one unit of another quantity.

Decimal forms aren’t required—unit rates can be whole numbers or fractions. And the numerator isn’t always 1; it represents how many units of the first quantity you have in that one unit of the second quantity.

So the true description is that unit rates express how many units of one quantity per one unit of another quantity.