How to Compare Unit Rates
A unit rate is a ratio expressing the quantity of one thing in terms of a single unit of another thing. For example, if you are paid $15 per hour, that's a unit rate that states how many dollars you get per time period. There are thousands of unit rates using many different systems of measurement, but they all follow the same pattern. It's vital for consumers to understand unit rates in order to get the most for their money. When a unit rate measures the amount of money a specific amount of a product costs, it is usually referred to as a unit price.
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Instructions
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Compare two items that have different unit rates. Consider the unit rate "miles per gallon" that measures automobile fuel efficiency. If one car has a unit rate of 22 miles per gallon and another a rate of 30 miles per gallon, the second car is more fuel efficient because you can travel farther for a given amount of gasoline.
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Convert unit rates from one system to another. This is often necessary because different systems are used to express equivalent unit rates. For example, suppose one aircraft flies 800 kilometers per hour (metric system) and another 520 miles per hour (English system). You need to convert one, so both unit rates use the same system in order to compare them. For speed, one mph equals 1.61 kph. Multiply 520 mph by 1.61 to get 837.2 kph.
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Know how to convert measures within one measuring system. This is especially helpful when shopping. For instance, you may see coffee advertised at $5 per pound. Another brand lists a unit price of 40 cents per ounce. To find out which is more expensive, multiply the per ounce unit price by 16 to convert to pounds: 16 x $0.40 = $6.40 per pound (you may do this in reverse by dividing the per-pound price by 16 to get 31.3 cents per ounce).
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Know how to create your own unit prices. To do this, divide the price of an item by the quantity. For example, if a whole chicken weighs four pounds and costs $7.20, the unit price is $7.20 divided by four pounds or $1.80 per pound.
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Tips & Warnings
You can purchase a unit-price calculator at most electronics stores. This is a great tool that can save you money when you shop.
