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Visually dividing unit fraction by a whole number

Learn how to divide fractions by whole numbers. You'll watch how dividing a fraction into smaller parts changes the denominator. Then, you'll practice this concept with examples to understand how dividing fractions works.

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  • blobby green style avatar for user manasvi27032010
    i cant understand the topic
    (8 votes)
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    • primosaur seed style avatar for user Ian Pulizzotto
      To divide a unit fraction by a whole number:

      1) Write 1 in the numerator.

      2) Write the product of the unit fraction’s denominator and the whole number, for the new denominator.

      Example: let’s divide 1/5 by 8.

      The numerator is 1.
      The new denominator is 5 x 8 = 40.
      The answer is 1/40.

      Have a blessed, wonderful day!
      (21 votes)
  • duskpin sapling style avatar for user Tasvib
    How would you show it on a number line, though?
    (10 votes)
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  • blobby green style avatar for user ayaan.yousufi
    How I do it is like this. For example 1/5 divided by 7. First write it down. 1/5 divided by 7. then you multiply by making the 7 a fraction like this. 1/5 divided by 1/7. Now just multiply 5 times 7. witch is 35. then just write the 1 on top of the 35. or just write the 1 first like this 1/35 and that is how you do it!
    (5 votes)
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    • blobby green style avatar for user kerrmaddox06
      Did you just type in division instead of multiplication? That’s a very bad mistake, and is little bit rare. Cause 1/5 divided by 1/7 is 7/5. To divide 1/5 divided by 7, you keep the dividend aka the one you’re going to divide, change the division symbol to multiplication, and flip the fraction. Since 7 can be written into 7/1, the reciprocal of 7 is 1/7. So you’re now onto 1/5 times 1/7. The rule of multiplying fractions is to multiply the numerators together and multiply the denominators together. 1 times 1 is 1 and for third graders, 5 times 7 is 35 because (5 times 5) plus (5 times 2) is 25 plus 10 which is 35. So the quotient which you correctly stated, is 1/35.
      (4 votes)
  • blobby green style avatar for user Chris Dugger
    Can you help me see why it's not 3/15? 1/5 divided by 3 equals logically 3 1/15ths. Why are we saying 1/15th I have autism and this is why I asking. Thanks!
    (3 votes)
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    • male robot hal style avatar for user Anonymous
      In fraction division (fraction divided by whole number) you have to leave the numerator untouched. You just go to the denominator. So if it is 1/4 (1 fourth) divided by 6 you MULTIPLY 4 and 6 (24) you just put 24 as the denominator and 1 as the numerator. If it is 5\9 (five-ninths) divided by 8 you MULTIPLY 8 and 9 (72) you put that as the denominator and leave the numerator the same(5) the answer would then be 5\72(five-seventytwoths) get it?
      (7 votes)
  • male robot hal style avatar for user Und3rsc0re
    This topic I find to be easy. But I have a harder time when it deals with bigger fractions like 75/1000. I need help with thos fractions.
    (5 votes)
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  • blobby green style avatar for user Chris Dugger
    I see 4/28 is 1/28 a simplified fraction?
    (3 votes)
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  • duskpin seedling style avatar for user SarahM
    This makes more sense now
    (2 votes)
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  • blobby green style avatar for user Sotha
    I understand that the pattern is to multiply the unit fractions with the whole number to approximate the correct answer. I don't understand the visuals explaining it though. I feel like I'm missing a key concept.
    (2 votes)
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  • blobby green style avatar for user arii
    so isn't it basically multiplying the denominator with the whole number?
    (2 votes)
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  • starky sapling style avatar for user 🔥👑💫@lina
    cant you just change them to fractions and divide it like that?
    (2 votes)
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Video transcript

- We are asked to figure out what is 1/7 divided by four, and they help us out with this diagram. We have a whole divided into seven equal sections. Each of those is a seventh, and we have one of those sevenths filled in, so this is 1/7 right over here, and then they divide it into four equal sections. In fact, they divide all of the sevenths into four equal sections, and so 1/7, which is this whole green bar divided by four, well what would be this fraction of the whole that is in a question mark. Can you pause this video and figure out what fraction of the whole is this question mark? When we divided the first seventh into four equal sections, we also divided all of the sevenths into four equal sections, and so now the entire whole is 28 equal sections because you have a four by seven grid. You have one, two, three, four rows and you still have your seven columns, and you can count them, seven, 14, 21, 28, and so 1/7 divided by four is going to be one of these 28 sections. This right over here is one over 28. This is 1/28. Let's do another example. We're told use the number line below to help visualize 1/5 being divided by three. As we go from zero to one on the number line, you can divide it into five equal sections where that's 1/5, 2/5, 3/5, 4/5, and of course 5/5 is equal to one, but we want 1/5 divided by three, so we took the section from zero to 1/5 and we divided it into three equal sections, and so the first of those sections, this one right over here, that would be 1/5 divided by three. What is this going to be equal to? Pause this video again and see if you can figure that out. The key realization is when we divided each of the fifths into three more equal sections, we can now think of each of these steps as a fifteenth because now we have one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15 equal sections between zero and one, and where did that 15 come from? We had five equal sections and then we split each of those five into three more equal sections so five times three is 15. This right over here is 1/15, this is 2/15, this is 3/15, which is equivalent to 1/5 and we can keep going on and on and on, but the key realization here is if I take that first 1/5 and if I divide it into three equal sections and I go only as far as that first of the three equal sections, that is going to be 1/15, 1/15 and we are done.