Tag Archives: unit rates

Multiplication Problems as Intro to Unit Rates and Slope (follow up)

I previously related elementary school word problems with math topics in secondary schools. The photo below shows a method to help elementary school students unpack the multiplication problem, to help middle school students identify the unit rate, and to help algebra students identify slope (you can focus on simple problems like this as an entry point to the linear function type problems).

In advance of this method, a review is conducted on the representation of multiplication using the groups of items model (below). By drawing a picture for the two parts of the problem that have a number, the students are guided to break the problem into parts and then to unpack the parts. The “5 boxes of candies” is represented by squares (or circles if you prefer) with no items inside. The “each box holds 6 candies” is represented by a single square with 6 items (dots) inside.

In turn, the drawing of the group of items leads to the multiplication statement, “6 candies x number of boxes.” I prompt students to include the items with the number as sometimes they will write this statement as “6 x number of candies”. I point out that 6 and candies go together. As seen in the previous blog post, the next step in this problem would be to replace “number of boxes” with the quantity given and then compute.

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Comparison Shopping – Real Life Example

Saw the following price tags, shown in the two photos, at an office supply store. $4 for 4 batteries or $9 for 8 batteries. To compare we can double the smaller pack to see that 2 packs would cost $8 for 8 batteries for a better deal.

Another method is to use unit rates. Rates are a measure of one quantity, with units, per 1 unit of another quantity, e.g. you make $10 per hour. To compute

$4/4 batteries = $1/1 battery  vs $9/8 batteries = $1.13/1 battery

2018-11-18 15.49.442018-11-18 15.49.40

Below is an example of instruction for unit rates to help a student conceptually understand (pretend that gas price shown on this pump is $2 per gallon). Say you pumped 3 gallons and it cost $6. Show the 3 1-gallon gas cans together and the 6 $1 bills together. Separate them to you have equal groups to get $ per 1 gallon. You can use actual gas cans (unused) or cutouts from Google Images.

gas price rate

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Unit Rates

yogurt unit rates

Real life applications in of themselves will not make a concept real for many if not most students with special needs. They likely need the concept broken down into more concrete form (CRA).

For this problem I would fudge the numbers and have 42 oz at $6 (7 oz per dollar) and a 5 oz at $1. I would have a photo of a “42” oz yogurt and cut it into 6 pieces and have 6 $1 bills and match each yogurt piece with a dollar bill to help students visualize the unit rate.

I took this photo tonight at Big Y and threw together this idea on the fly.

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