Get ready for 5th grade
Learn to multiply a 3-digit number by a 1-digit number using regrouping. In this video, we will multiply 7x253. Created by Sal Khan.
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- okay so a lot of people say that the new way of this generation's math is very easy but it is actually very complicated. The old way is a lot easier so you schools that are doing great1(26 votes)
- Has anyone ever wondered 4 digit by 4 digit(16 votes)
- how do you solve it with 10 digits?//(5 votes)
- What is 305 x 6?(3 votes)
Multiply 300 by 6 which is 1800. Now you know your answer is at least 1800.
Next multiply 6 by the remaining number 05 which same as 5. 3x5 is 30. Add your two answers and you'll get 1830 :)(4 votes)
- he said at0:42'carry appropriately' can you carry inappropriately(4 votes)
- did anyone else notice that he said one thousand seven hundred AND seventy one? The proper grammar is one thousand seven hundred seventy one.(3 votes)
- yeah i noticed that as well i'm kinda surprised he made that mistake since hes the one teaching us grammar(2 votes)
- my brother is 13 but has 5th grade(3 votes)
- What is the biggest number's name like maybe 99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 is the biggest?(2 votes)
Let's multiply 7 times 253 and see what we get. So just like in the last example, what I like to do is I like to rewrite the largest number first. So that's 253. And then write the smaller number below it and align the place value, the 7. It only has a ones place, so I'll put the 7 right over here below the ones place in 253. And then put the multiplication symbol right over here. So you could read this as 253 times 7, which we know is the same thing as 7 times 253. And now we are ready to compute. And there are many ways of doing this, but this one you could call the standard way. So what I do is I start with my 7. And I multiply it times each of the numbers up here, and I carry appropriately. So first I start with 7 times 3. Well, 7 times 3 we know is 21. Let me write that down. 7 times 3 is equal to 21. You could do this part in your head, but I just want to make it clear where I'm getting these numbers from. What I would do in the standard method is I would write the 1 into 21 down here, but then carry the 2 to the tens place. Now I want to figure out what 7 times 5 is. We know from our multiplication tables that 7 times 5 is equal to 35. Now, we can't just somehow put the 35 down here. We still have to deal with this 2 that we carried. So we compute 7 times 5 is 35, but then we also add that 2. So it's 35 plus 2 is 37. Now, we write the 7 right over here in the tens place and carry the 3. Now we need to compute what 7 times 2 is. We know that 7 times 2 is 14 from our multiplication tables. We can't just put a 14 down here. We have this 3 to add. So 7 times 2 is 14, plus 3 is 17. So now we can write the 17 down here, because 2 is the last number that we had to deal with. And so we have our answer. 7 times 253 is 1,771.