4th grade (2018 edition)
- Multiplying 2-digit by 1-digit
- Multiplying 3-digit by 1-digit
- Multiply without regrouping
- Multiplying: 2-digit by 1-digit (regrouping)
- Multiplying 3-digit by 1-digit (regrouping)
- Multiplying 4-digit by 1-digit (regrouping)
- Multiply with regrouping
- Multiplying 2-digit numbers
- Multiply 2-digit numbers
Learn to multiply a 4-digit number by a 1-digit number. In this video, we will multiply 8085 times 9. Created by Sal Khan.
Want to join the conversation?
- can u do the same thing or concept for billion(5 votes)
- why are there negitive numbers?(5 votes)
- You can imagine that negative numbers mean something owed. It's not that you can hold negative something, but rather you need to take that number from something else. For example I have 25 apples and you want 5. So 25-5 = 25 + (-5) represents you taking the 5 from me.(7 votes)
- if you change the places will you need to do more work then you orignaly did (im bad at spelling sorry)(5 votes)
- Yep! It's ok that you aren't good at spelling as long as others can understand you, and I can.(4 votes)
- so 5x2 is like 2+2+2+2+2 so 5x2=10 so 2+2+2+2+2 ok i can do that?(5 votes)
- i need to learn my fact in my head(4 votes)
- the multi digit multiplication is so easy and now i under stand it better than before.(2 votes)
Let's multiply 9 times 8,085. That should be a pretty fun little calculation to do. So like always, let's just rewrite this. So I'm going to write the 8,085. I'm going to write the 9 right below it and write our little multiplication symbol. And now, we're ready to compute. So first we can tackle 9 times 5. Well, we know that 9 times 5 is 45. We can write the 5 in the ones place and carry the 5 to the tens place. So 9 times 5 is 45. Now we're ready to move on to 9 times 8. And we're going to calculate 9 times 8 and then add the 4 that we just carried. So 9 times 8 is 72, plus the 4 is 76. So we'll write the 6 right here the tens place and carry the 7. Now we are ready to calculate, and I'm looking for a suitable color. 9 times 0 100's plus-- and this is a 7 in the hundreds place, so that's actually 700. Or if we're just kind of going with the computation, 9 times 0 plus 7. Well, 9 times 0 is 0, plus 7 is 7. And then, finally, we have-- and once again, I'm looking for a suitable color-- 9 times 8. This is the last thing we have to compute. We already know that 9 times 8 is 72. And we just write the 72 right down here, and we're done. 8,085 times 9 is 72,765. Let's do one more example just to make sure that this is really clear in your brain, at least the process for doing this. And I also want you to think about why this works. So let's try 7 times 5,396. And I encourage you to pause it and try it on your own as well. I'm going to rewrite it-- 5,396 times 7. First, we'll think about what 7 times 6 is. We know that's 42. We'll put the 2 in the ones place. 4 we will carry. Then we need to concern ourselves with 7 times 9. But then, we have to calculate that and then add the 4. 7 times 9 is 63, plus 4 is 67. So we put the 7 down here and carry the 6. Then we have to worry about 7 times 3 plus this 6 that we had just finished carrying. 7 times 3 is 21, plus 6 is 27. So we'll write the 7 here in the hundreds place and carry the 2. And then, finally, we have 7 times 5, which is 35. But we have to add the 2. 35 plus 2 is 37. So 5,396 times 7 is 37,772.