Multiplying 9s Strategy - MyTutoringBee

This video is for parents and teachers who want to learn some new ways to help their students learn multiples of 9!

A lot of students know the 9s trick with counting fingers, but did you know there are other ways to memorize your 9s multiplication facts?! I will show you 3 different ways that 9s multiplication facts are so cool and have neat patterns which will help you remember them!

I work with students all the time on multiplication practice, and every student has their favorite way to remember them. Which one is yours?

Transcript

0:01
Hey everyone! I am here to show you a couple of quick, easy tricks for multiplying your nines. When you’re learning your nines facts, there are a couple of ways that can help you remember them—or at least figure them out if you don’t already have them memorized.

0:16
As you can see, I already have all of my nines facts from 9 × 1 through 9 × 10 listed out here with their answers. If you look, you can see the pattern.

0:30
In the tens place, all of the numbers are ascending. And then if you look at the ones place, they do the opposite.

0:42
So this is a quick, easy way—when you are listing out your facts—to remember them.

0:48
Okay, there are a couple other things about the nines that are really neat, I think.

0:57
Also, when you add the digits of any nines fact from 1 through 10 together, they will equal 9.
So:
0 + 9 = 9
1 + 8 = 9
2 + 7 = 9
…and so on.

1:17
This only works with the nines. It doesn’t work with any other number.

1:27
Okay, and here’s another little fact: the tens place will actually be one less than the number that you are multiplying by 9.
So:
0 is 1 less than 1
1 is 1 less than 2
2 is 1 less than 3
…and so on.

1:47
That can be a little clue for you when you’re actually trying to figure out your nines facts.

1:52
Like, let’s say you’re trying to figure out 9 × 8. Well, I know that 7 is one less than 8, and then 7 + 2 equals 9. So you can kind of combine those two little tricks to help you quickly remember your products when you’re trying to multiply nines.

2:11
And then there is one more trick that does not require pen and paper. It actually requires your hands!

2:20
Let’s take, for example, 9 × 3. What I’m going to do is start at the left and work my way to the right, just like we do when we’re reading.

2:30
I tell my kids: start here and count to the number that you’re multiplying by. So since I’m multiplying 9 × 3, I’m going to count 1, 2, 3—and I’m actually going to bend that third finger down.

2:42
Now, if you look, I have two fingers on this side of the bent finger, and then seven fingers (including these two and these five) on this side. So my answer is 27.

2:55
And it works for any of these facts that are on this paper here.

3:00
For example, if we want to do 9 × 9:
I’m going to start again at the left and count all the way across. This time it’s going to transfer over to my right hand.
1, 2, 3, 4, 5, 6, 7, 8, 9.
I put the ninth finger down.

3:16
I’ve got eight fingers on this side of the bent finger and one finger over here on the right. So my answer is 81.

3:24
It works on all of them—even 10. Most kids know their 10 facts. Once they start multiplying, it’s pretty easy to pick that up.

3:33
But even with 10, once you get down to the 10th finger, you put your thumb down. You’ve got nine on this side, none on the other side. That’s 90.

3:42
So that works really well when you don’t have pencil and paper and you don’t have the time to list all of these facts.

3:49
That’s another easy way for you to remember your nines facts.

3:53
Thanks so much for watching my video!