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Studying for a test? Prepare with these 8 lessons on Module 3: Multi-digit multiplication and division.

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# Multiplying: 2-digit by 1-digit (regrouping)

Video transcript

Let's try to compute 6 times 37. And I'll show you one
way of doing this. And then in future
videos, we can look at other ways of
doing this and think about why this is
actually working. So what I like to
do-- and this is often called the standard
method-- is take the larger of the two numbers. It doesn't matter if you're
doing 6 times 37 or 37 times 6. They equal each other. 6 times 37 is the same
thing as 37 times 6. So what I like to do is I take
the larger of the two numbers, and I write it on top. So I'll write 37. And then the smaller
of the two numbers, which is 6, I'll write
it on the bottom. And I'll align it by
the correct place. This only has one digit. It's in the ones
place, obviously. So I can write the
6 right over here. And I'll write the
multiplication symbol like that. And this is just another way
of expressing 37 times 6, which is the same thing as 6 times 37. Now, what we do is
we go with this, the first place in
this lower number. And there's only one place here. It's only the number
6 right over here. And we're going to multiply
that times each of the digits up here. So first, we will
start with 6 times 7. So we're going to first
multiply 6 times 7. Well, you remember from
your multiplication tables, 6 times 7 is equal to 42. Now, we don't just
write 42 here. At least, not in
the standard method we wouldn't write 42 here. We'd write the 2 in
42 in the ones place. So we'd write that
right over there. And then we'd carry the 4
in 42 up to the tens place. Now we need to think
about what 6 times 3 is. Well, once again,
we know 6 times 3. 6 times 3 is equal to 18. But we can't just
write an 18 down here. We still have this
4 to deal with. So 6 times 3 is 18, but
we've got to then add the 4. So 6 times 3 is
18, plus 4 is 22. So it's 6 times
3, and then we're adding that 4 right over there. And that's how we get
our answer-- so 222.