I have turned to several books to challenge students and get them excited about math. Math Detectives is one I wrote about several months ago that I use to challenge K-3 students. Cool Math is another one I have written about that I use to challenge students in grades 3-6.
Today I want to share with you a new favorite book and a lesson I did with a group of students based on one of the ideas in the book.
Near the beginning of the book, there is a history of some of the ways numbers have been written in the past. If you know any Egyptian or mathematical history, you know the Egyptian numbers were quite complicated and required quite a few symbols to write each number.
Because of this, multiplication was challenging for the Egyptians so they developed this great strategy for multi-digit multiplication based on the idea of doubling. I showed their strategy to my students and they worked together to see if it always seems to work and to figure out why it works.
Check out some of the problems
Here is another one
|This one made for easy doubling and easy addition!|
Now that they had the process down, we started thinking about why it works
|Here kids made the connection that the 188 across from the 4 represented 4 groups of 188. The 752 across from the 16 represents 16 groups of 47.|
Now they pull it all together
|Here is where students REALLY got what was happening and were able to write it out and talk about how it represented the distributive property. I also had a student who was able to show how it connected to using an array.|
This lesson led to a great discussion about multiple strategies for multi-digit multiplication and how some strategies are more efficient than others and how the numbers in the problem change the efficiency of some strategies.
How do you challenge kids who are ready for it?
Looking for a great book on teaching multiplication? Check out this post!
Here is a fun way to practice double digit multiplication.