## Using Excel for Problem Solving

One of the more enduring lessons that I do with my algebra class is having them use Excel for problem solving. Don't know why I haven't written about it as I've been teaching this strategy for at least 5 years now. (I don't recall reading other teachers' blogs about using Excel this way either. Please let me know if you do!)

Hand-Holding: I pose this familiar — 5th grade? — problem to my 8th graders.
There are 53 horses and cows in Farmer Johnâ€™s farmyard.  There are 21 more cows than horses.  How many of each type of animal are there?
I let them work on it for a few minutes. Most will share that they use guess-and-check. Then I just have them watch and listen as I solve it via Excel. After that, they grab their laptops, along with this printed instruction, and try to repeat the process. The problem is intentionally easy so they can just focus on entering information and simple equations into the cells — get acquainted or reacquainted with spreadsheets.

You Try: Then I give them this problem to try on their own.

For a play, the ticket prices were \$5.00 per child and \$8.50 per adult. The children bought 100 more tickets than the adults. The total box office income was \$905.00. How many tickets of each type were sold?

I let them struggle on this and encourage them to help each other. About 10 minutes later, I step in to guide them by asking lots of questions. We arrive at one possible way to set this up in Excel. (I hid rows 8 through 25.)

Have Fun: I give them this sheet of 16 problems and ask them to choose just 3 or 4 to work on.

Extension: It's also great to use Excel to solve problems like "Daniel and the Devil"...

The devil made a proposition to Daniel. The devil proposed paying Daniel for services in the following way:

"On the first day, I will pay you \$1,000 early in the morning. At the end of the day, you must pay me a commission of \$100. At the end of the day, we will both determine your next day's salary and my commission. I will double what you have at the end of the day, but you must double the amount that you pay me. Will you work for me for a month?"

Or "Salary Plans"...

You just got a job at Jimmy's Skateboard Shop. You have a choice of two different salary plans.

Plan A Earnings: \$120 per week plus 10% of sales

Plan B Earnings: \$90 per week plus 15% of sales

You can expect your average sales per week to be \$400. Which salary plan is better?

For most retailers, the months of November and December bring in a lot more sales than usual. Say you can expect your sales per week to be \$1,000 during these two months, then how would this influence your decision on which salary plan to go with?

I love it when my kids ask if they may use Excel to solve problems, especially when we get to systems of equations. Yeah, one more strategy in their toolbox!

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• October 6, 2012 4:08 PM Myrna wrote:
THANK YOU!!! Can't wait to try this!
1. October 6, 2012 5:15 PM fawnnguyen wrote:
You're so welcome, Myrna! Thank you!
• October 6, 2012 4:58 PM Kristin wrote:
I use it for the allowance problem of \$20 per month or 1 cent the first day, 2 the next, 4 the next....continuing to double. I like your instructions. Thanks!
1. October 6, 2012 5:17 PM fawnnguyen wrote:
Thanks for dropping in, Kristin!
• October 6, 2012 7:53 PM Sue VanHattum wrote:
I never heard of the Daniel and the Devil one - sneaky! (I give my students 1 cent on day one, double each day, or \$100 on day one, with each day being \$100 higher than the previous.)
1. October 7, 2012 9:24 AM fawnnguyen wrote:
It is sneaky, huh? This type of problem is where I see Excel being used in the classroom, but Excel can be used in a lot more context. Thanks, Sue.
• October 7, 2012 3:42 AM Nathan Kraft wrote:
I love using Excel in math class, especially since it is my go-to tool for just about everything I do.
I'll definitely use your 16 problem worksheet, although I may have to spread some of this out over the course of a year. There is definitely a variety in challenging problems, and all of them are good. I'd want my students to attempt most of them at some point.
Again, thanks for sharing.

1. October 7, 2012 9:19 AM Nathan Kraft wrote:
Another great way to use Excel is for scatterplots/lines of best fit. Because really, who does this by hand anymore?
1. October 7, 2012 9:32 AM fawnnguyen wrote:
Exactly! @ratzelster just wrote a post this morning on using it for line of best fit. This is where my kids' knowledge of Excel comes from, using it in science class and for their science project. Funny, you came to mind, Nathan, when I wrote the post because of what you shared for SBG grading -- your Excel work.

I should say that we do return to the 16 problems throughout the year! I love them and wouldn't want them to go to waste. So glad you could use them!! You're welcome and thank you!

• October 7, 2012 10:11 AM crazedmummy wrote:
Now teach them how to use "solver" in excel and explain how it works... :-)
• October 14, 2012 11:16 AM Robbie Shaw wrote:
Plan to use this later in the year with my gifted sixth graders. Hope I can remember it/
1. October 14, 2012 10:02 PM fawnnguyen wrote:
Yeah, good to know, Robbie! Thanks for dropping in.

• November 2, 2012 10:58 AM Kristin wrote:
So we tried your lesson today, but my students need a lot more handholding after the first problem. any tips to get them to work on their own?
1. November 4, 2012 11:08 AM fawnnguyen wrote:
I'd do another problem with the whole class. Then let them struggle, quietly on their own, then have them talk with another person. They both can struggle, it's good for them. Your hand-holding should be in the form of asking lots of questions that will guide them to think about what it is they want the software to do. They WILL get it, Kristin, especially if the next problem they try on their own is similar to the one the whole class did with you. They need to persevere and we need to be patient. I think this is worth the time. Thanks for letting me know.
• March 5, 2013 8:24 PM Andrew Stadel wrote:
Thanks Fawn! This is a great way for me to get my students to use Excel.
1. March 5, 2013 10:44 PM fawnnguyen wrote:
You're very welcome, Andrew! I'm always trying to get kids to do more with Excel, love the instant feedback: wrong input = wrong output!