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## Topic B: Foundations

Current time:0:00Total duration:2:31

# Subtracting mixed numbers with like denominators

## Video transcript

Let's figure out what 11 and
12/16 minus 5 and 8/16 is. And then we might have
to simplify it down to lowest terms. So the way I like to do these
is to kind of separate out the whole number
part of the mixed numbers from the
fractional part. So I can rewrite this
number right over here as 11 plus 12/16. And from that, I am
going to subtract-- and I'll put parentheses
here because I'm going to break this part open. I'm going to
subtract 5 plus 8/16. 5 and 8/16-- same
thing as 5 plus 8/16. But I have to remember,
I'm subtracting it. I'm subtracting
this whole thing. So I could rewrite it as--
I'll rewrite this part-- 11 plus 12/16. And I'm subtracting 5 plus 8/16. So I can distribute
the negative sign. So it's going to be minus
5, negative 1 times 5. And then negative 1
times positive 8/16. So it's going to be minus 8/16. And then I like to do the
whole number parts separately and then the fractional
parts separately. So let's do the
whole number parts. We have 11 minus 5. I'll write it here, 11 minus 5. We'll do that part. That's the whole number part. And then we have plus 12/16. Let me do this in pink maybe,
plus 12/16, minus 8/16. And 11 minus 5 is 6. And I have 6 plus. And then our denominators
are the same here, so we're going to get
something over 16. And 12 minus 8 is 4. So this is the same
thing as 6 plus 4 over 16, which is the
same thing as-- writing it as a mixed number-- 6 and 4/16. And this is the right quantity,
but we can simplify it. 4/16 can be simplified. Both the numerator and the
denominator are divisible by 4. They both have the factor 4. So let's divide both the
numerator and denominator by 4. Divided by 4. Divided by 4. Since we're dividing
by the same thing, we're not changing its quantity. And so this is
equal to-- we still have the whole number part,
6, but the fraction part is now 1, 1/4. So we get 6 and 1/4.