Percent Math Game

I’m writing this blog as a resource for any others who like math and games. It’s a math game. The math group that meets bi-weekly has really enjoyed playing, so I thought it would be fun to share with others.

We have started working how to calculate percent, and I thought it would be fun to play a game with some real life scenarios involved. This game helps you practice calculating tips at a restaurant, sales tax, and how much money off when something is on sale.

Materials: 

  • Playing Cards, printed on blue, white, or green card stock
    • White: Restaurant cards – make receipts & scenarios. You can see my examples in the link, but I suggest using restaurants your students would actually go to with items they recognize. Making people they know the waiters/waitresses in the scenarios can be fun too.
    • Blue: Sales tax cards – look up what the sales tax is in your state.
    • Green: On sale cards – I used items that I thought the kids would like to buy.
  • Game Board with green, blue, and white spaces. We just printed this on paper and laminated it.
  • Die

Mini lesson before playing:

I asked if the kids notice at restaurants that their parents leave tips for the servers. All of them knew this. I asked them if they knew how much most servers make, and some didn’t realize how little their hourly wage was. I explained that this is why it’s customary to tip here in the states. Not all cultures have this practice though, which I also told them about.

I let them know that it’s common to give 18% gratuity. Having been a server before, I told them that I would always leave a tip, even if the service wasn’t great because I know how hard it is. I also know that sometimes it’s the kitchen who messed up, not the server. I explained that it would have to a terrible experience for me to leave only 10%, and many times I tip 20%.

Then I said, “If I told you that I was happy about 90% of the time, does it mean that I am happy most of the time?” I gave a few other examples like this to reinforce the concept that a percent is part of a whole. Anything over 50% is more than half of the whole, 25% is a quarter of the whole, 20% is 1/5, 75% is 3/4, and other benchmarks like this.

Then we went over strategies to calculate percent. I like reminding the kids that there are many ways to find answers to mathematical problems. I tell them that different strategies are like tools you put in your toolkit. You can use different ones in different orders to figure out what you want to figure out. Sometimes I may give them a tool, sometimes they come up with one, sometimes they learn it from a peer, or their parents. To me, it’s really fun to try out different ways to figure out problems.

The strategies we came up with:

  1. The Halving Strategy: It’s easy to halve any number. Then you can find 50%, 25%, or 12.5% or 6.25%

If you are estimating, this works just fine. Let’s say you want to leave a 18% tip, and the bill is $45. Half of $45, or 50% is $22.50. Half of that, or 25% is 11.25. Half of that, or 12.5% is about $5.62. Picking a number between 20% and 12.5% will get you close to 18%.

2. The Ten Percent Strategy: It’s easy to find 10% of any number by moving the decimal place to the left one time. If your bill is $4, 10% is 4.50, and 20% is just that number, doubled, or $9, so you can calculate a 20% tip like that.

You could do this for calculating any percent off as well. If something is discounted 30%, well, multiply 10% by three.

You can use this strategy to find 5%. Just halve 10%. If sales tax is about 5%, well find 10%, halve it, and you have the 5% tax.

3. Multiplication: Using a calculator or paper and pencil, you can just multiply to find the answer. The kids in this group have spend time practicing the multiplication algorithm. While I’ve shared the strategy of just counting up how many decimal places there are in the problem and making that the same in the answer, I prefer for them to first estimate and make sense of the problem and decide where the decimal point goes logically.

For example, if you are finding what 85% of 60 is, I have the kids say what the answer would be close to. In this example, it’s going to most of the number, 50% of 60 is 30, and 100% of 60 is 60, so the number is inbetween 30 and 60.

If you use paper and pencil to multiply 85 x 60, you get 5100. Where does it make sense to put the decimal place? The only logical place is 51.00 because that is between 30 and 60.

Of course, using a calculator you would just type in .85 x 60 🙂

 

How to Play:

The kids take turns rolling the die. The color they land on determines the card they take, whether it’s a receipt & scenario card, a tax card, or a sale card.

The rule we use is that no one helps unless they ask for help, and we create space and time for people to think. Some do all the calculation in their heads and some use paper and pencil.

img_20170206_112230
We have been having “picnic math” where we lay out a blanket and eat and play this math game.

 

Variations: 

  • Ditch the board and kids just pull the cards they want. The kids I work with love the restaurant cards and just taking turns with these back and forth.
  • Create variations that are for different skills. I have receipts that have no cents and receipts with cents and the kids choose the difficulty level they want to have.

What I like about the restaurant cards is that the kids choose the percent they tip. A child can tip 50% if they want, and that’s fine and easy to calculate. Some kids want to make it hard for themselves to figure out so they will choose 18%, or even something like 6%. So starting with just restaurant cards would be a good way to go if you have someone in your group that is hesitant to calculate in front of people.

Fortunately, the vibe with the kiddos I am working with is really supportive. They like challenges and it’s not a big deal to get problems wrong. I think this game has been big hit because it involves real life situations they they have encountered before. I’ve had kids sharing with me that they have asked to calculate their parents tips at restaurants and this is so fun to hear!

I think playing this game as often as the kids want is great for several reasons:

  • It solidifies the understanding that fractions and percents are a part of a whole.
  • They get to practicing using easy benchmark fractions/percents with a variety of numbers.
  • They are making logical sense of the situation around the calculations so they are not just following step by step rules to solve a problem, but also making sense of what they are doing.

Later we will move on to doing more with fractions, but this game gives them lots of practice so they can understand part-whole relationships that I can help them build on.

If you try the game out, let me know in the comments. If you know other strategies you want to share, also type that in the comments!

Leave a Reply

Your email address will not be published. Required fields are marked *