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Home > MC1 > Chapter 9 > Lesson 9.3.3 > Problem 9-151


Unit rate is defined as rate with a denominator of unit. If a sprinter runs meters in seconds, her speed per second can be calculated as shown below. (Note that this was the world record set in 1988 by Florence Griffith-Joyner at the US Olympic Trials.)

 gives , so she ran meters each second. This is a unit rate. 

In addition, the number of seconds it takes her to run each meter can be calculated as gives , so it took her seconds to run each meter.

  1. An ice skater covered meters in seconds. Find his unit rate of speed in meters per second.

    meters per second

  2. A train in Japan can travel miles in hours. Find the unit rate of speed in miles per hour.

    Follow the steps in part (a) and in the example above.

  3. Alaska has a very low population density. It only has people in square miles. Find the unit rate of density in terms of people per square mile.

    About people per square mile.

  4. New Jersey has a very high population density. It has people per square mile. If Alaska had the same population density as New Jersey, what would be the population of Alaska? Solve with a proportion. (By the way, there were about people in the United States as of the year 2009.)