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### Course: Arithmetic > Unit 10

Lesson 4: Multiplying fractions and whole numbers word problems# Multiplying fractions word problem: milk

Sal solves a multiplication fraction word problem about milk. Created by Sal Khan.

## Want to join the conversation?

- how is 6/1 = to 6(0 votes)
- because 1/1 is equal to 1 whole so 6/1 is equal to 6(9 votes)

- I got confused about something about halfway through. How exactly does 20/5 equal 4??(0 votes)
- 20 ÷ 5 = 4. If the fraction is improper check if you can divided the numerator by the denominator.

Happy to help!(7 votes)

- because 1/1 is equal to 1 whole so 6/1 is equal to 6(2 votes)
- is 2/9 equal to 1/3(1 vote)
- I still don't get it

What do you meen(1 vote) - I got confused about something about halfway through. How exactly does 20/5 equal 4??(0 votes)
- is the 1 in the beginning of the video under the 6 (6/1) supposed to make it easier or can it be optional? (is it necessary?)(0 votes)
- Yes it's necessary because you may forget that you need to multiplied the six by the other top number and the one by the bottom number but if you didn't have the 1 you might forget to leave the bottom number alone and might accidentally multiply it also by six and end up getting the problem wrong. So I guess it is not completely necessary but it is good to have there as a extra little tool to help you not mess up on the problem. I hope this helped you please get back t o me if it didn't or if you have any other questions about this or any other topic in khan adademy. I will answer it in the best way I can. 😃(5 votes)

- Is 6/1=6 because it’s a improper fraction?(0 votes)
- why divide by 5? why can't you divide by 2 or 3 or 25 or any other number(0 votes)
- How did you change the 100 into a 78(1 vote)
- I think that he added, or multiplied, subtracted, or divided.(0 votes)

## Video transcript

If there are 6 people
in your family, and each person drinks 4/5 of
a gallon of milk each month, between what two whole numbers
is the number of gallons of milk your family
will drink each month? So let's think about
this a little bit. So I've got my milk gallon
here for inspiration. So there's 6 people
in my family, or in your family, whoever's
family we're talking about. And each of them drink
4/5 of a gallon per month. So we're going to go 6
times 4/5, or 4/5 times 6. Now, what is this
going to be equal to? Well, there are several ways
we could think about this. One, we can express
6 as a fraction. We could say that this is the
same thing as 6/1 times 4/5. And you multiply the numerators. You multiply the denominators. 6 times 4 is 24. And 1 times 5 is 5. So 24/5 gallons are going
to be drunk every month. And this is the same
thing-- let's see, 5 goes into 20 evenly
and has a remainder of 4. So we could write this
as 20/5 plus 4/5 5-- let me move over a little
bit so I don't run out of space, which
is the same thing. This is 4. So this is 4 and 4/5. So that's one way
to think about it. The other way, you could
think of this as 4/5 times 6, which is the same thing
as 4/5 plus 4/5 plus 4/5-- I think you get the idea--
plus 4/5 plus 4/5 plus 4/5. We took literally six 4/5's
and added them together. And what's this
going to be equal to? Well, this is going to
be 4 plus 4 plus 4 plus 4 plus 4 plus 4 over 5. This is how many 1/5's we have. Well, this is 6
times 4, or you could say 4 times 6, over 5,
which is equal to 24 over 5, which we've already
figured out is 4 and 4/5. So either way,
we're going to drink 4 and 4/5 gallons per month. Now let's try to answer
the actual question. Between what two whole numbers? Well, between 4 and
5 gallons a month. 4 and 4/5 is right
in between 4 and 5. We got it right.