Monday, September 14, 2009

Life skillz: Shopping

(the z makes it cool)

For about 3 years between high school and college I worked as a cashier at a grocery store. If I had a dollar for every time someone came through my line and spent way more than they thought they were going to...(Wait, scratch that, I technically did make a dollar every time this happened)  Anyway, from that experience I realized that many adults have trouble estimating the amount of money they spend when going shopping.

I decided my students could use some help with the matter.  So, I went to the grocery store to buy some things for a cookout and video taped parts of the experience.  It was really busy there, so the video didn't come out that great as I was trying to avoid getting anyone on camera. (Converting for youtube didn't do the video any favors either)  This is the finished product:
Granted adding and estimating isn't complex math, but students have no trouble in seeing the activity's use in everyday life.

I had some extra time at the end of class on Friday in two of my classes, so I told them we would have a competition.  Of course, the winner would receive candy.  I didn't tell them what the contest was (though it became pretty obvious), I just told them to pay close attention and to follow these rules:
  1. No talking
  2. No writing anything down during the video
I stopped the video before it gave the answer, and told them to write their guess for the total on a small scrap of paper.  Many of the answers were pretty off (up to about a $20 difference), and surprisingly my 9th graders guessed considerably closer than my 12th graders. (Which made me feel better about taking their class time for it)  Then we did some discussion where we talked about estimating and general paying attention.  Despite the lack of complexity, it was definitely a worthwhile activity. It certainly was an eyeopener for those whose guesses were way off, and all of the kids really got into it.

Anyone have any ideas on how to extend this to add some higher level math and make a full lesson out of it?


  1. I was going through this video for an activity with my class and these are the numbers my students came up with for the prices:


    Where did they go wrong?

  2. Excellent question, to which there is a strangely complicated answer. I'm not sure if this is the same in all states, but in PA there is a tax on some foods but not others. Foods deemed non-necessary (snacks, soda..) are taxed. It made for a fun math problem for me to solve to figure out which of my foods were considered snacks. Turns out it's the Gatorade (I think this has to do with percentage of fruit juice) and the coolwhip. With PA's 6% sales tax, that makes the numbers work out. Hey, I think I just figured out how I could extend the lesson!

  3. Thanks for the additional information!