In the previous example, a unit rate was used to convert from one currency to another. Converting values into common units make comparisons possible.

Example 3

An Olympic runner has a resting heart rate of 45 beats/minute. An amateur athlete has a resting heart rate of 9 beats for every 10 seconds. Compare the amateur's resting heart rate to that of the Olympian.

Convert both heart rates to the same unit of time, either in beats per 10 seconds or beats per minute.

Convert the amateur's heart rate to beats per minute.

The Olympian's heart rate is lower, at 45 beats/minute, than the amateur's heart rate, at 54 beats/minute.

Converting unit rates is another way to compare rates when both measures in one rate are different from another rate. For instance, the cost of gasoline in Canada versus the United States is compared in the following example.

Example 4

In April 2013, the cost of gasoline in one city in the United States was 3.58 USD/gallon. At the same time, the cost of gasoline in a Canadian city was 1.12 CAD/L.

In April 2013, were the Americans or the Canadians paying more for gasoline?

1.00 CAD = 0.9894 USD
1 US Gallon = 3.79 L

For comparison purposes, the units must be the same.

One method is to convert the American funds and imperial measure to Canadian funds and metric measure.

Convert 3.58 USD/gallon into CAD/L.

Step 1: Convert American currency (USD) to Canadian currency (CAD). Let x = value in CAD.

3.58 USD/gallon is equivalent to 3.618 CAD/gallon.

Step 2: Now convert from gallons to litres.

Step 3: Compare the cost of gasoline in the two countries now that the units are the same.

Americans pay $0.95/L and Canadians pay $1.12/L.

The Canadians pay more for gasoline.