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## 4th grade (2018 edition)

### Unit 2: Lesson 3

Multi-digit multiplication: standard algorithm- 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

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# Multiplying 2-digit by 1-digit

Learn to multiply a 2-digit number by a 1-digit number without regrouping. In this video, we will multiply 32x3. Created by Sal Khan.

## Want to join the conversation?

- What is 32 x 45?(7 votes)
- You can do it by yourself. If you really don't know how to multiply multi digit numbers, then let me demonstrate. First, you multiply 32x5 and then add a zero at the ones place and do 32x4 and add the numbers. So that's the answer.(10 votes)

- At0:08Sal says he likes to have the bigger number on top, but you can have them the other way round can't you.(7 votes)
- I also like to have the bigger number on the top.(4 votes)

- My name is Miranda Clarke.I like math but i can get confused on it some time.how do we tell if it is grater or less then.(4 votes)
- i like to think of the signs like an alaligators mouth or a crocks mouth. the gator or the crock both want more.

i hope this helps!(1 vote)

- How would you do 3 digit numbers?(3 votes)
- hi guys it is my birthday(4 votes)
- That was a awesome video!(4 votes)
- yea that is how you do it for (3*30)+(3*2) and i rater do it on paper(4 votes)
- this is kind of hard can someone help me?(3 votes)
- This is very good,But i still don't understand can someone please explain beacuse i have a test soon.(2 votes)
- i don't get it 3x30+3x2(2 votes)

## Video transcript

Let's try to
calculate 3 times 32. And I like to rewrite it, and
this is one way of doing it. I like to rewrite it where I
have a larger number on top. So in this case it's 32. And I write the smaller
number right below it. And since the smaller
number is only one digit, it's only a ones digit, I
put that below the ones place on the larger number. So I'll put the 3
right over here. And of course, we can't forget
our multiplication symbol. And this is essentially a
way of saying the same thing. You could read
this as 32 times 3. But 32 times 3 is the exact
same value as 3 times 32. It doesn't matter what
order you multiply in. Now let's try to compute it. And once again, this is
only one way of doing it. There's many ways of doing it. And I want you to think
about why this works. We'll start with
this 3 down here, and we're going to multiply it
times each of the digits in 32. So we'll start with 3 times 2. Well, 3 times 2 from our
multiplication tables, and you can figure it
out even if you didn't know your multiplication
tables, is 6. So 3 times 2, I'll write 6 right
over here in the ones place. Now we're going to figure
out what 3 times 3 is. Well, once again, we
know that 3 times 3 is 9. And since I'm multiplying times
the tens place right over here, I'm going to put it in the
tens place right like this. So we're done. We got 32 times 3 is 96. And I really encourage you to
think about why this worked. And I'll give you a
little bit of a hint here. I'll give you a little bit of
a hint about why this worked. Remember, 3 times 32 is the
same thing as 3 times 30 plus 3 times 2. And if you look at
it that way, that's essentially what
this process did. We did 3 times 2 is 6. 3 times 30 is 90. You add them together,
you get 90 plus 6 is 96.