Ratios and Proportions / Intro to Rates

Understanding

Students develop the concept of a unit rate and how to use it to compare amounts in given different ratios.

What to look for

As students explore unit rates, remind them that to find equivalent ratios, they must multiply or divide both terms of the ratio by the same positive number.

Sample Assessment

It took 7 hours to mow 4 lawns, each with about the same area.

a. What is the rate at which lawns were being mowed? 
Answer: (7/4) hours to mow one lawn or 1 and (3/4) hours per lawn.

b. How many lawns could be mowed in 35 hours? 
Answer: 20 lawns

The Big Idea

Every ratio has an associated unit rate. The unit rate is the numerical part of the rate; the “unit” in “unit rate” is the 1 in “1 per student,” “for each 1 minute,” or “for every 1 cup.”

What are the students doing?

Students should pay attention to the words used to describe a rate such as per and each.

What is the teacher doing?

Work with students to explore how to partition one remaining bag of dog food into fractions of a bag so that it can be distributed among the dogs. Have students explore different ways to share the bags of dog food when they have fewer bags of dog food than number of dogs.