Friday, October 14, 2016

Breaking Apart Multiplication

As we move to multiplying larger numbers, I like to guide them into the algorithm. We start by investigating the pattern when multiplying by multiples of 10. We look at the problems 2 x 3 = 6, 2 x 30 =60, and 2 x 300 = 600. We discuss what is the same/different about each problem, then we look at several other similar examples. Eventually the kids see the pattern of just "adding a zero" each time. Patterns are a great shortcut, but it's important the kids understand why they work.
Next we move to breaking apart larger multiplication problems, such as 18 x 5. We can break the 18 into 10 and 8 to help us multiply easier.

We practice this with many numbers, also looking at the array model for each. We slowly get to larger numbers like this one...
This will lead us into the multiplication algorithm next week.