SHOW TOCHIDE TOC

section 5-2
 

Unit Rates and Proportional Reasoning

 

Lesson Preview


What You'll Learn

  1. To find unit rates
  2. To use unit prices

… And Why

To find speed, as in Example 2


Finding Unit Rates

A rate is a ratio that compares two quantities measured in different units. Suppose you read 233 words in two minutes. Your reading rate is fraction with numerator 233 words and denominator 2 minutes.

The rate for one unit of a given quantity is the unit rate. To find a unit rate, divide the first quantity by the second quantity. For a reading rate of fraction with numerator 233 words and denominator 2 minutes, the unit rate is 116.5 words per minute.

Video Math
thumbnail showing the first frame of accompanying video clip

Calories

Play Video

3.7 MB

Example 1 Finding a Unit Rate

A box of cereal contains 8 servings and has a total of 36 grams of fat. Find the unit rate of grams of fat per serving.

detail via d link.d

The unit rate is fraction with numerator 4.5 grams and denominator 1 serving, or 4.5 grams per serving.



The model below shows the relationships in Example 1.

detail via d link.d

You can express speed as a unit rate involving a unit of time. Sometimes the time is given in more than one unit, such as minutes and seconds. Convert the time to a single unit, such as seconds, to find the speed.

Example 2 Real-World globe Problem Solving

SportsIn 2001, Justyna Bak of Poland set a world record for the women's 3,000-m steeplechase. Her time was 9 min 25.31 s. What was her speed in meters per second? Round your answer to the nearest hundredth.

  1. Convert the time to a single unit.
     
    detail via d link.d

Her time was 565.31 s.

  1. Write the ratio of meters to seconds. Use a calculator to divide.
     
    detail via d link.d

Justyna Bak's speed was 5.31 m/s.



Course 2 iText

Page

Chapter 5
Ratios, Rates, and Proportions