Teaching Unit Price in Consumer Math Class

One of my favorite units to teach in Consumer Math is the one on unit pricing. Once I started paying attention to pricing at the grocery store, I was amazed at just how often unit prices were wrong. Here is a photo of a couple bottle brushes:


Surely the value 2-pack is cheaper, right? Nope! I can get 1 bottle brush for $2.04 or a pack of 2 bottle brushes for $4.29. My students didn't think this one was a big deal because it was "only a few cents". I then explained to them that it was THEIR few cents! I went back to the store for months seeing if the pricing was changed (because surely it was an error) and it stayed as is. In fact, it's 2 years later and the pricing is still the same.


Here's another example of the value size not actually being cheaper. It's hard to see, but in the left photo each mac and cheese is $1. The right photo shows 2/$5 or 4 mac and cheeses for $5. Without checking unit pricing, my assumption would have been the 2-packs were cheaper. 


Value Size is no value
Before teaching consumer math I had assumed that all value sizes were [duh, obviously] a better deal than the smaller sizes. Not so! 


On the top shelf is the "Hot Deal"! You get 48 pencils for $7, or a little less than $0.15 per pencil. Down on the much less spectacular "less list" are packs of 12 pencils for $0.68, or a little over $0.05 cents each. I bought a bunch of the smaller packs. I'm not ashamed.


Sometimes the pricing is just all wrong for no reason at all
My daughter used to like these squeezy veggie pouches before she became a bit obsessed with applesauce. The green ones. Not the blue ones. The GREEN ONES. THE GREEEEEN ONES!!!!!


Using the orange unit prices, it looks like the single-pouches are a better deal and this situation neatly fits into the "I'm not getting scammed" category. I mean, $5.27 per unit is clearly better than $5.49 per unit. But before we move on, let's use our unit price formula to check those unit prices...


It turns out the 4-pack is a better deal even though the unit prices show otherwise. Tricky.


I don't even know what to say about this cheese. I love this store, but there's no way $7.99 for 12 slices is sometimes $9.32 a pound and other times $9.99 a pound. 


Just no. That's the same price.


The prices on these popsicles totally confused me. All I wanted was some relief from the heat. I ended up just buying both and calling it a day. 


Unit pricing is not standardized
Many times I've stood in aisles scratching my head at the pricing of two comparable products. 


Sometimes the units used in the unit pricing of one product are different from the units used in the comparable product. This makes it difficult or impossible to compare the two. In that photo of eye drops up there, the drops on the left use "ounces" in the orange unit price. 

The eye drops on the right use "per 100 count" in the orange unit price. The eye drops on the left are your typical eye drops in a bottle while the ones on the right are those single use ones. While it's nice that the unit prices are there, they're not actually helpful. It's impossible to compare these two products because we'd need to know how many single-use drops are in an ounce. 

Here is a short Youtube video on how unit pricing at the grocery store is far from standardized.


Now these eyedrop labels are much more helpful. Wouldn't it be great if all labels were like these?


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Every year I teach my Consumer Math students how to make a checkbook register in ExcelIt's how I keep track of bills and I use it in place of a paper register. None of my students use a paper register to keep track of their ATM withdrawals. Lots overdraw and get the $30/day fee! 


Keeping track of spending on the computer is much more appealing, and they can choose to make theirs in a Google Sheet instead or Excel. The activity is a free download here.



I also recently put together a financial literacy word wall that works to support a consumer math curriculum. 


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