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.)

Hand-Holding

I pose this familiar — 5th grade? — problem to my 8th graders.

There are 53 horses and cows in Farmer John’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 set of 16 Excel 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!