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Multiplication tables for 10, 11, 12

Learn to multiply 10, 11, and 12 using 'times tables.'. Created by Sal Khan.
Video transcript
In the last video we went over the multiplication tables for 1 through 9 and I ran out of time, and actually, it was a good thing because 1 through 9 are kind of the core multiplication tables. And you'll see that if you know all your multiplication tables from 1 to 9, so you know any number between 1 and 9 times any other number between 1 and 9, you can actually do any multiplication problem out there. But what I want to do now is I want to complete the multiplication tables for 10, 11, and 12. So what is 10 times-- let's just start with 0. 10 times 0. Anything times 0 is 0. Ten 0's are 0. 0 plus 0 plus 0 ten times is still 0. What's 10 times 1? Well that's just 10 one time. Or 1 plus itself ten times. That's 10. I think this is second nature to you at this point. What's 10 times 2? I meant to switch colors, but I didn't. 10 times 2? That's 10 plus 10, which is 20. Fair enough. And notice, we went up by 10 the first time. We went up by 10 again to get to 20. What's 10 times 3? Well, that's 10 plus 10 plus 10, or we could view it as 10 times 2 plus another 10, which is equal to 30. What's 10 times 4? I think you start to see a pattern. 10 times 4 is equal to 40. Notice, 10 times 4 is equal to 40. If I were to tell you what is 10 times-- let me do another color-- 5? Well that's equal to 50. 10 times anything is that anything with a 0 behind it. So the 10 times tables you almost don't have to remember it. So let's just keep going. What's 10 times 6? It's equal to 60. 6 0. What's 10 times 7? 70. 10 times 8? This is almost ridiculous. 10 times 8 is 80. 10 times 9? 90. 10 times 10? Now this is interesting. So it'll be a 10-- let's see me write this. Let me do it in this orange color. 10 times 10. So it'll be ten 10's or a 10 with a 0 behind it. There you go. Notice everything-- whatever times 10 I just add a 0 and then I get the next number. So it's 100. And I think you understand why that is. I added 10 to itself ten times. That each 10-- you go from 10, 20, 30. 30 is just three 10's or 10 times 3. 90 is just nine 10's or 9 times 10. Let's keep going. So 10 times 11 is equal to 11 with a 0 behind it. 110. Finally, 10 times 12 is equal to 120. Now, just for fun, these are kind of your 10 times tables. But now that t know the pattern you can do anything. If I asked you what 5,732 times 10 is, what's it going to be? It's going to be this number with just one more 0. So it's going to be-- I won't read it out yet. 5 7 3 2 with a 0 behind it. And just so you know, this little comma that I wrote in the number there, that's just to make it easier for me to read that number. And you put the comma-- you start over here and every third number you put the comma. So here I'm going to put the comma right here. I'm going to put the comma right there. So now I can read this. The comma doesn't really add or take anything away from the number, it just helps me read it. Now 5,732 times 10 is 57,320. i just had to add a 0 there, but that was a pretty straightforward multiplication. And notice, we had 5,000 times 10 and we got to 50 something thousand when we multiplied them. So that's similar to 5 times 10 is equal to 50. But instead of 5 I had a 5,000, and so I got a 50,000 and something and all this other stuff. We're going to learn more about how to do problems like this in the future. But I thought I would introduce you to the idea that just from this little pattern of adding a 0 you already know your 10's times tables. Now let's do our 11's. Well, they start off easy, and then they get a little more difficult as we get into high numbers. 11 times 0. This is easy, this is 0. 11 times 1. This is also easy. It's 11. 11 times 2. We're going to start seeing a pattern here. It's 11 plus 11 or we could've added 2 to itself eleven times, but that is equal to 22. If we do 11 times 3 it is equal to 33. 11 times 4 is equal to 44. I think this is becoming obvious to you. What's 11 times 5? 11 times 5 is 55. Notice I put the 5 twice. What's 11 times 6? It's 66. 11 times 7 is 84-- no. I'm kidding. I didn't want to mess with you like that. But no. Of course, it's 77. You just repeat the number twice. Let me switch colors. 11 times 8 is equal to 88. 11 times 9 is equal to 99. Now what's 11 times 12? Oh sorry, I skipped 10. 11 times 10. You might want to say it's 1,010. No. That's wrong. It's not 1,010. So that little pattern that we had where you just repeat the number, that only worked for one-digit numbers. So it only worked for 1 through 9. 11 times 10? Well, we could think about it a couple of ways. We can add 11 to 99. So we can say it's 99 plus 11. And what's that? That's equal to 110. And I'm going to show you how to do-- well, hopefully you've already watched the video on how to add two-digit numbers like this, but that's 110. Or you could just use the property from the 10's times tables that we learned where if you just take 11 times 10 you add a 0 to the 11, you get 110. That's the 11 right there. Finally, let's do 11 times 12. No easy way to remember this, you just kind of should remember it. Or you could say look, it's going to be 11 more than 11 times-- sorry. I keep skipping things. We should do 11 times 11 first. Let me make sure this is clear. We're doing 11 times 11 before we go to 11 times 12. So 11 times 11 is going to be 11 more than 11 times 10. So we add 11 to this. 11 plus 110 is 121. And actually, as you'll see, there actually is an order as we get to higher multiples of 11, but I'll leave that to a future video. And then finally, we're at 11 times 12. And we could add 11 to itself twelve times. We could add 12 to itself eleven times. Or we could just say, hey, is going to be 11 more than 11 times 11. So that is what? You add 11 to this. What do you get? You get 132. I just added 121 plus 11 and then got 132. Now the other way you could have said it is, well, what's 10 times 12? We already knew that. That was 120. So 11 times 12 because we're multiplying 12 by one more should be 12 more than that. So that should be 132. So two ways to get the exact same answer. All right, now let's do our 12 times tables. And once you know this you are ready to tackle any type of multiplication problem. But we'll do that in future videos. So 12 times 0. Super easy. 0. 12 times 1. Also super easy. Is 12. Now it gets interesting. We're going to increase by 12 every time. 12 times 2 is equal to 24. 12 plus 12 is 24. 12 times-- not 22. Let me rewrite that. 12 times 3 is going to be 12 plus 12 plus 12. Or we could write that as 12 times 2. I see my brain is doing the wrong things. We could rewrite that as 12 times 2 plus 12. Or we could rewrite that as 24 plus 12. Either way, all of these get us to 36. And notice, that's just that plus 12. 12 times 4. 12 times 4 is equal to 48. There's a lot of ways you could think about it. You could say 11 times 4 is 44. And you go up by one more 4, so you get to 12 times 4. Or you could say 12 times 3 is 36 and you can add one 12 to it to get to 48. Either way works and that's because you can multiply in either direction. Let's keep going. 12 times 5 is equal to 60. 10 times 5 is 50, 11 times 5 is 55, so 12 times 5 is 60. 12 times 6 is equal to what? It's going to be 12 more than this. It's going to equal 72. 12 times 7. 12 more than this again. 12 more than 72 is 84. And I'm serious, I'm probably a lot older than you are and I still, in my head to confirm, I go to some 12 times tables that I remember as definitely right. Like oh, 12 times 5-- and sometimes in my head I say, oh, let me add another 12. Oh yeah, definitely, my memory was correct. 12 times 6 is 72. All right. Then you go to 12 times 8. Add 12 to the 12 times 7. 96. 12 times 9 . Well you add 12 to this, so it's 108. And then 12 times 10. This is an easy one. We just add a 0 to the 12 to get 120. Or we could've added 12 to 108. Either way. 12 times 11. We just did this. You add 12 to this you get to 132. And then 12 times 12 is equal to 144. And this actually shows up. If I had a dozen of a dozen eggs-- a dozen is 12. Or if I had, I think a gross is actually 12 dozens. So that's 144 eggs. You'll actually end up seeing this number a lot. More than you would expect in life. But anyway, we've now completed all of our multiplication tables. And I really encourage you to take the time now to go and memorize them. Make some flash cards. Use the little software thing that I wrote on my website. You could try that out. As of September 2009 it's working. I haven't touched it in a while, but I'm actually probably going to rebuild it soon. So if you're watching this video in the year 2200. Well, I would probably not exist anymore. But hopefully you'll get a better version of the software app. But you should practice it. You should get your parents to quiz you. You should get notes cards. You should just be mumbling to yourself as you walk to school-- what is 12 times 9? What is 11 times 11? And you should quiz each other because it'll pay huge rewards to you later on in life. See you in the next video.