What do the following multiplication facts have in common? More importantly, how can knowing some of the smaller facts help you know the larger facts?
You hear a lot of talk about using strategies to learn basic facts, but I’m not sure it’s always clear what that means.
Most kids will know 2 x 3. If you ask them how, they’ll probably tell you they skip count by twos, or they know it’s 2 groups of 3 (or 3 groups of 2), or they add 3 + 3. Remember, it is really important to ask students how they know, because even with a very simple fact, there’s are lots of ways to see it.
Let’s move on to 4 x 3. Well, 4 is double 2, so wouldn’t 4 x 3 be double 2 x 3? Another way to look at it is that 2 x 3 is 2 groups of 3 and 4 x 3 is double that. Learning the 4s facts by doubling the 2s is a great strategy.
How about 4 x 9? Some kids might use a friendly number here, because 9 is so close to 10. So they’d do 4 x 10 and then just subtract one group of 4 to get 36. Another student might notice that 9 is 3 times as big as 3, so 4 x 9 must be 3 times as big as 4 x 3. Again, getting 36. Still another student might see 2 x 9 and 2 x 9. Still 36. 🙂
Finally, we get to a toughie–8 x 9. I was always SO bad at that one! Again, you could use a friendly number (8 x 10) – 8. Or you could double 4 x 9.
I’m sure there are lots of other ways to look at these problems, and therein lies the beauty–yes, beauty– of number talks. Getting the kids to talk about, and listen to, multiple fascinating strategies.
If you’re looking for a resource to learn more about strategies for multiplication and division, check out Mastering the Basic Math Facts in Multiplication and Division: Strategies, Activities & Interventions to Move Students Beyond Memorization. Long title, but a really easy to use book!