Lesson 2: Understand Rates and Unit Rates6.AT.2

I can…

I can describe a rate using its two different units and use a model to find a travel time, and I can find a unit rate to compare prices and decide the better buy.

Key words

• Rates and Unit Rates — A rate compares two amounts. A unit rate is for 1.
• Rate — Two amounts compared, like miles for each hour.
• Unit Rate — The amount for just 1 of something.
• Per — For each one, as in 5 dollars for each book.
• Ratio — A way to compare two amounts, like 3 to 2.
• Unit price — The cost of just one item, like $0.60 a game.
• Better Buy — The choice that costs less for each item.
• Divide — Split a total into equal groups.
• Constant — A number that stays the same.
• Total price — What the whole package costs.

Steps

1. Booth A charges $3 for 5 games. I want the cost for just 1 game.
2. I divide the cost by the games: $3 ÷ 5 = $0.60.
3. So Booth A costs $0.60 per game. That is the unit rate.
4. Because this unit rate is money for one item, it has its own name: it is the unit price.
5. Now I can compare this booth's unit price fairly with any other booth's.

Try it

A snack stand sells 4 juice boxes for $3.00 or 6 juice boxes for $4.20. Which deal is the better buy?

Check your answer

6 for $4.20 — $0.70 each

$3.00 ÷ 4 = $0.75 per juice box. $4.20 ÷ 6 = $0.70 per juice box. $0.70 < $0.75, so 6 for $4.20 is the better buy.

Sentence starter

I know ___ because ___.

Goal: I can explain a rate like "150 miles per hour" using distance and time units, and explain my choice using the words rate, unit rate, per, and better buy.