Definition: A unit rate is a rate in which the second quantity is exactly one unit, such as 55 miles per hour or 4 dollars per pound.
What is a unit rate?
A unit rate tells you how much of the first quantity there is for exactly 1 of the second quantity. The phrase per 1 is the signature. Examples include 12 dollars per hour and 3.5 liters per minute.
How do you find one?
Divide the first quantity by the second quantity. Suppose a bakery sells 18 muffins for 13.50 dollars. The price per muffin is 13.50 divided by 18, which equals 0.75 dollars. Check: 18 times 0.75 is 13.50.
When is it useful?
Unit rates make comparisons fair. If Store A sells 5 notebooks for 6.25 dollars and Store B sells 8 notebooks for 9.60 dollars, compute each price:
- Store A: 6.25 divided by 5 is 1.25 dollars each.
- Store B: 9.60 divided by 8 is 1.20 dollars each.
Store B is the better buy.
What is a common error?
Dividing in the wrong order. Divide by the quantity you want to be per 1. For miles per gallon, divide miles by gallons, not gallons by miles.