Multiplication

Thie blog will help with how to demonstrate multiplication using manipulatives. The rule for multipling whole numbers is: For any whole numbers r and s, the product of r and s is the sum occuring r times. Written out as such:
r * s = s + s + s .... + s -- r times
In our manipulative kits we can find the rectangular objects to help demonstrate this rule.
If we were to use a rectangle with 6 units on it, and place 5 of them in a row, it would then show 6 + 6 + 6 + 6 + 6 = 30. Then, take all 6 rows and place them into one large rectangle. This would give you a 5 X 6 shape indicated 30 units. As future teachers I find this to be a great example to use in the classroom to students who have a hard time understand why 6 * 5 = 30.

Using models for mulitplication algorithms can be used with larger numbers as well. Using base 10 pieces, we can see the relationship that numbers hold together when multipling.
Let's do the example for the text book (pg 166)
3 x 145

The number 145 is shown in model pieces and tripled because we multipling 145 by 3.
Grouping together all the flats, longs and units we will then see 4 flats, 3 longs and 5 units. This is because some longs became flats, units became longs and so on.

Using models is always a good example to share with people :)