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## Dividing fractions by fractions

Current time:0:00Total duration:2:08

# Dividing whole numbers & fractions: t-shirts

CCSS.Math:

## Video transcript

A baby's T-shirt requires 4/5
yards of fabric, or 4/5 of a yard of fabric. How many T-shirts can be
made from 48 yards? So what we want to do is we
essentially want to say how many groups of 4/5 of a yard
can we make with 48 yards? So you literally view this as
we want to take 48 yards and divide it into groups of 4/5
of a yard, and say how many groups are there? Because each of those
groups can make one to baby's T-shirt. If you give me 4/5 of a yard,
one baby's T-shirt, so the number of groups of 4/5 is the
number of babies' T-shirts. Now, when we divide by a
fraction, we just have to remember that that is the same
thing, that is completely equivalent to multiplying
times the reciprocal of the fraction. So if we have 4/5 here,
that'll be 5/4, the reciprocal. Now, you still might say, hey, I
have a whole number here and a fraction, and you just have
to remember any whole number can be written as a fraction. This is the same thing
as 48/1 times 5/4. Now, we could just multiply it
out at this point and figure out what 48 times 5 is and
that'll be over 4, but that'll get big numbers and it'll be
hard to kind of divide and all that, but we could divide at
this stage right here. We could divide the numerator
and the denominator by 4. Or we could say, look, this is
going to be equal to 48 times 5, whatever that is, over 4. Now, let's divide the
numerator by 4. Well, we could divide 48 by 4,
and we will get to 12, and whatever we did to the
numerator, we have to do to the denominator, so if we
divide 4 by 4, we get 1. So then we're left with 12 times
5, which is equal to 60. 12 times 5, which is equal to
60/1, which is the exact same thing as 60. So you can actually make 60
children's or babies' T-shirts from 48 yards if each of
them use 4/5 of a yard.