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All courses Math Foundations · MF.PR.2 16 of 60
Compute and interpret unit rates, including rates with fractional or decimal quantities.

Find a unit rate from whole numbers

Problem
A car travels 180 miles in 3 hours. What is the unit rate in miles per hour?
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Hint

Set up the rate as miles divided by hours: 180 miles ÷ 3 hours, since the question asks for miles per 1 hour.

A unit rate tells how much goes with exactly 1 of the second quantity. For miles per hour, divide miles by hours and keep the units in that order.

Solution walkthrough

01

Identify the per-1 quantity

\[180~\text{miles}~\text{in}~3~\text{hours}~\rightarrow~\frac{180\text{ miles}}{3\text{ hours}}\]

The question asks for miles per hour, so we want the number of miles that go with 1 hour. That means divide miles by hours.

02

Divide to find miles for 1 hour

\[180~\div~3~=~60\]

Splitting 180 miles equally across 3 hours gives 60 miles in each 1-hour part.

03

Attach the correct units

\[60\text{ miles in }1\text{ hour}~=~60\text{ miles per hour}\]

A unit rate must be written with exactly 1 of the second quantity. Here that second quantity is 1 hour.

04

State the unit rate

\[60\text{ miles per hour}\]

The car’s unit rate is 60 miles per hour.

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Another way

  1. Use a rate table and divide both values by 3: 180 miles in 3 hours becomes 60 miles in 1 hour.

!

Common mistake

Dividing in the wrong direction, like 3 ÷ 180, or writing 60 hours per mile. The problem asks for miles per hour, so miles must be divided by hours and the units must stay in that order.