Incan Quipu Math (place value, history)

During the Inca empire, a system of knots was used for adding numbers. We've been reading about it in a fascinating math/activity/history book,  The Secret Life of Math; discover how (and why) numbers have survived from the cave dwellers to us!

We did a little quipu activity and quickly figured out why this math method--though effective--didn't last to the present day. At least not if everyone was as bad at knot tying as we are! ;) It is, however, a fun activity to explore history and reinforce knowledge of place value.



Inca Quipu Math activity

Materials needed:

a thin dowel or chopstick
thin cord
colored markers
scissors
paper/pencil (optional)

Procedure:

1. Tie four long cords onto the dowel. If the cord is too short, you won't be able to tie many knots, so leave yourself plenty of room. The three cords to your right are the addends, the cord on the left is the summation.

2. Though the Incas didn't do this, we added colored marks on the cord so we could easily see the divisions between each place value grouping. As you tie knots the cords won't continue to line up evenly, but it will help you be able to see that the hundreds are between the orange and purple marks, etc.

3. Decide on three numbers you'd like to add. Tie knots on your cord to represent the numbers. For example, on the cord on the far right (below) we chose the number 2,133. This is represented by two knots in the very top section, one knot in the next section, three knots in the third section, and three knots in the bottom section. We made number cards just to help us remember what we were doing. (Later it was fun to mix and match the cards with the cords!)

4. Add the knots in all the ones sections on all three cords. Record the total number of ones on the summation cord. For us, the ones totaled 11; therefore, we put 1 knot in the ones section and 1 knot on the tens section on the summation cord. Continue through each subsequent place value section.

We did this activity during a study of Inca history. My student, age 7, found it difficult to tie the knots, so I did most of the tying. He did the adding and writing. When we finished he said, "That was FUN!"

Another place value game that my children enjoy from time to time...Learning Resources Dino Math Tracks Place Value Game. Here's the Amazon product description:

"Prehistoric pals make this award-winning math game a blast. Roll the dice and move the dinosaurs around a delightfully illustrated game board. Learn all about numbers - from counting, addition and subtraction to place value skills. Includes game board, 16 dinosaurs, cards, number die and instructions for various levels of play. For 2 to 4 players."

I also found a little online activity to practice identifying place value in a number.