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## 5th grade

### Course: 5th grade > Unit 7

Lesson 4: Dividing whole numbers by unit fractions# Dividing a whole number by a unit fraction

Sal uses a fraction model to divide a whole number by a fraction.

## Want to join the conversation?

- One thing I don't understand, when we divide 3 by 1, we get a result of 3, but when we divide 3 by 1/4 we a get a number higher than 3, I'm kind of confused, can someone explain?(6 votes)
- When we divide 3 by 1, we are trying to find how many 1's there are in 3. In this case, there are 3 ones in 3. The same goes when we divide by fractions, when we divide 3 by 1/4, we are trying to find how many 1/4's there are in 3. There are 4 quarters in 1, so there must be 3 times as many quarters in 3 than there are in one. 4 times 3 is 12, so there are 12 1/4's in 3. Another way to think about this is to use logic. 3 divided by 1 is 3. 3 divided by 2 is 1.5. So we can see that the answer gets smaller as the divisor gets larger, therefore, the answer must get larger as the divisor gets smaller. Hope this helps!(41 votes)

- So, do you basically do the whole number times the denominator of the unit fraction to get your answer?(22 votes)
- Why can't I vote for you? I don't even know why we are vote?(1 vote)

- all you need to do is just multiply the whole number by the denominator(8 votes)
- Yes, but I would like to point out that if the number has a numerator that is not one, you need to do it the way Mr. Sal shows you. :)(2 votes)

- I have found that if you do the whole number times the denominator you can usually get the correct answer, but I've only done it on simpler problems. Does this process always work?(4 votes)
- Yes, when dividing a whole number by a unit fraction, multiplying the whole number by the unit fraction's denominator always works!

This is because, for any numbers a and b with b nonzero, we have

a divided by (1/b) = a times (b/1) = (a/1) times (b/1) = ab/1 = ab.

Have a blessed, wonderful day!(4 votes)

- It is easy 3 divided 1/4 is just doing 4x3(5 votes)
- how would you divide a whole number by a fraction when it's not 1/2, 1/3,1/4

for example 2 / 5/6. In a different module on proportions, the answer they give is a mixed numeral, but I can only get a fraction: 5/12(5 votes) - Im in seventh grade and i cant figur it out gfkbhvjchdfjcgm(4 votes)
- When dividing fractions like 1/9 divide by 4, you only need to do 1/ 9 x 4 = 1/36(4 votes)
- This is essentially correct. Revise the last equation to say 1/(9 x 4) = 1/36, to make it clear that 9 and 4 are multiplied first.

Have a blessed, wonderful day!(1 vote)

- "SAL MAKE BRAIN AAAAAAAAAAAAAA"-Albert Einstine.(3 votes)
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## Video transcript

- Lets think about what three divided by one fourth is equal to. Pause this video and see if you can figure it out on your own. And I'll give you a
hint, take three wholes and divide it into pieces
or sections that are each one fourth of a whole and then think about how many sections you have. Alright now lets work
through this together. Now let me draw three wholes. And so lets say this is... I'm gonna hand draw it, so
its not gonna be perfect. But lets say that is one
whole right over there. This is two wholes right over there. And then I have my third
whole just like that. And now I'm going to divide it into pieces or sections that are each
one fourth of a whole. So this first whole is four pieces that are each one fourth
each, of four fourths. And then I have another four
fourths right over here. And then I have another four
fourths right over here. Another way to think about
it, I took the three wholes, and I divided it into fourths. So if you divide it into fourths how many pieces am I going to have? Well this is pretty straight
forward, you have one two three four five six seven
eight nine ten 11 12 pieces. And I didn't even have to count that, each whole is gonna be four fourths. So three wholes is going to
be three times four fourths, or 12 pieces or 12 sections. So that is going to be equal to 12. Another way to think about
it is if you take three and you divide it into equal
sections that are each a fourth you are going to have 12 equal sections.