Unit rate is an important topic in middle and high school. Unit cost (e.g., hamburger meat on sale for $2.39 per pound or you make $13 per hour) is an example of unit rate. This post shows how to use unit cost as an effective entry point to learning unit rates.
Significance
First, unit rates and unit costs are common in life. Second, in the Common Core State Standards math categories you can see that Proportional Relationships, and Ratios and Proportions (which includes unit rate) are a 6th and 7th grade topic and are then replaced by Functions in 8th grade. The proportional relationships are an entry point for functions.
Below is a photo showing a graph of a function. The slope of a line is the ratio of vertical change to horizontal change. In context, it can model the unit rate in a proportional relationship.
Unit cost can be challenging for students who need life skills math
Activity
First, I present a pack of items the student likes (4 pack of Muscle Milk for this student). Use a Jamboard to show a 4 pack and the price of the 4 pack (photo on left). Then I “pull out” the 4 individual bottles and divide the $8 among the bottles to show $2 for each bottle. Here are links to a FB Reel and a YouTube video showing how this works.
I Follow the same steps for ounces or pounds but show how 4 oz is divided into single ounces (in lieu of a pack divided into single items). Then the student shops for items that can easily be divided to get a unit cost.
Google Document
A follow up to the Jamboard is to have students use a scaffolded chart to shop for items. This will help them internalize conceptually what a rate and unit rate are.
Have them start with an item that is a pack. In the Google Document, they paste a screenshot, enter the cost and quantity, and then compute and enter the unit cost but use “for 1” before delving into volume and weight.
Accessing Jamboard
You have to make a copy of the Jamboard in order to use it.
