## Friday, February 26, 2016

### Adding and Subtracting Positive & Negative Numbers with a Zipper Bag

What can you do with a gallon-size zipper plastic food storage bag? Believe it or not, you can practice adding and subtracting positive and negative numbers!

This can be mighty confusing for kids and rather than worksheet them to death, why not grab a bag, and play a little game?

My son and I had lots of fun with this and played for quite some time.

What You Need
A plastic gallon-size zipper food storage bag for each player
PDF of number line and die (download free from Google Drive here)
die
heavyweight card stock to print the PDF on
Scissors
Glue
fine-tip permanent black marker

Preparation
Print as many copies of the first page of the PDF as you have players. Trim each end so it just fits into our zipper bag.

With the marker, make a small line in the center of the bag's zipper pull.

Print the page with the die onto another sheet of heavyweight card stock. Trim the two dice templates, fold, and glue (I use a hot glue gun).

How to Play
Players should place the zipper pull with the mark lining up with the zero. This is where everyone starts. Player 1 rolls all three dice (the add/subtract, the -/+, and the number die). This will tell the player what their equation is. For example if they roll ADD, negative (-), and four, they will need to solve the problem
0 + -4 =

They'll then move their zipper slider to -4.

Now it's the next player's turn to roll the dice, solve the equation, and move the slider on their own bag.

The first player to reach either end of the timeline (i.e. 19 or -19) first is the winner.

Need a refresher on how to solve these equations? Check out Khan Academy's great online tutorial here.