This lesson introduces the term unit rate and the two unit rates, and , associated with a ratio . Students learn that each unit rate tells us how much of one quantity in the ratio there is per unit of the other quantity. They also see that, although both unit rates describe the same situation, one or the other might be preferable for answering a given question about the situation.

The work in this lesson also reinforces the idea that dividing one number in a ratio by another is an efficient way to find a unit rate. (It is not necessary to start with a table or use another representation as an intermediate step.)

In explaining how two unit rates can describe the same situation, students practice justifying their reasoning and critiquing the reasoning of others (MP3). As they calculate unit rates, interpret them in context, and decide on a unit rate to use to solve a problem, students practice reasoning abstractly and quantitatively (MP2).