Fraction multiplication on the number line

Name: Fraction multiplication on the number line
Uploaded: 2019-09-06T19:41:16Z
Description: Sal uses number lines to help solve multiplication equations.

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Sal uses number lines to help solve multiplication equations.

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Lilliyana
Posted 4 years ago. Direct link to Lilliyana's post “I only understand this a ...”
I only understand this a little bit not alot but a little bit 😗
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(16 votes)
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Rayray😘
Posted a year ago. Direct link to Rayray😘's post “Can 3-7 work?”
Can 3-7 work?
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(2 votes)
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- Saranya Rijju
  Posted a year ago. Direct link to Saranya Rijju's post “that would be -4”
  that would be -4
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  (5 votes)
claireh30
Posted a month ago. Direct link to claireh30's post “:) This is easy for me”
:) This is easy for me
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(2 votes)
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- 😀Samuel Hobaugh😀
  Posted 8 days ago. Direct link to 😀Samuel Hobaugh😀's post “super easy for me to:)”
  super easy for me to:)
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  (1 vote)
😀Samuel Hobaugh😀
Posted 8 days ago. Direct link to 😀Samuel Hobaugh😀's post “everyone have a blessed w...”
everyone have a blessed wonderful day
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KyLeIgH
Posted a month ago. Direct link to KyLeIgH's post “idk what that means can y...”
idk what that means can you put it in a different way maybe
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Leroy.robinson
Posted a month ago. Direct link to Leroy.robinson's post “i like khan akadmey”
i like khan akadmey
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(1 vote)
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- 😀Samuel Hobaugh😀
  Posted 8 days ago. Direct link to 😀Samuel Hobaugh😀's post “you spelled Khan academy ...”
  you spelled Khan academy wrong I also love Khan acadmey
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  (1 vote)
mantunez13
Posted 2 years ago. Direct link to mantunez13's post “i kinda understand but i ...”
i kinda understand but i there another way to do this cause it's hard to understand
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(1 vote)
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- joaopaulovf
  Posted 19 days ago. Direct link to joaopaulovf's post “A simpler way to do this ...”
  A simpler way to do this is by multiplying the whole number by the numerator (top or left number) of the fraction.
  
  For example, 4 x 2/3:
  4 x 2/3 = (4 x 2)/3 = 8/3
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  (1 vote)
m.diazso
Posted 2 days ago. Direct link to m.diazso's post “is there other way to do ...”
is there other way to do this
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Queen Johnna :)
Posted a month ago. Direct link to Queen Johnna :)'s post “Have a good day!”
Have a good day!
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(1 vote)
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- 😀Samuel Hobaugh😀
  Posted 8 days ago. Direct link to 😀Samuel Hobaugh😀's post “you too:)”
  you too:)
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  (1 vote)
Mila
Posted 6 months ago. Direct link to Mila's post “What if it takes too long...”
What if it takes too long to draw the number line can’t you just times the numerator by lets say three
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(0 votes)
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Video transcript

- [Instructor] So, what we're gonna think about in this video is multiplying fractions. So, let's say that we wanted to take 2/3 and we want to multiply it by four, what is this going to be equal to? Pause this video and try to think about it on your own. Alright, now let's work through this together. And, to help us, I will use a number line, and let's say that each of these hash marks represent a third. So, this is zero, this is 1/3, 2/3, 3/3, 4/3, 5/3, 6/3, 7/3, 8/3, and 9/3, and so where is 2/3 times one? Well, 2/3 times one is just going to be 2/3, we just take a jump of 2/3, so that is times 1. If we multiply by, or if we take 2/3 times two, that'll be two jumps, so one 2/3, two 2/3, three 2/3, and then four 2/3. So, we just took four jumps of 2/3 each. You could view that as 2/3 plus 2/3 plus 2/3 plus 2/3, and where does that get us to? It got us to 8/3. So, notice, 2/3 times four is equal to 8/3. Now, we could go the other way, we could look at a number line and think about what are ways to represent what the number line is showing us? And, on Khan Academy, we have some example problems that do it that way, so I thought it would be good to do an example like that. And, so, let's label this number line a little bit different. Instead of each of these lines representing a third, let's say they represent a half, so zero, 1/2, 2/2, 3/2, 4/2, 5/2, why did I write 5/6, my brain is going ahead, 5/2, 6/2, 7/2, 8/2, and 9/2. And, let's say we were to see something like this. So, if you were to just see this representation, so I'm going to try to draw it like this, so if you were to just see this representation, what is that trying to represent? What type of multiplication is that trying to represent? Well, you could view that as 3/2 plus another 3/2 plus another 3/2, 'cause, notice, each of these jumps are three 1/2, or 3/2. So, you could view this as 3/2 plus 3/2 plus 3/2, or another way of thinking about it is this is three jumps of 3/2. So, you can also view this as doing the same thing as three times 3/2, and what are these equal to? Well, 3/2 plus 3/2 plus 3/2, or three times 3/2, it gets you to 9/2.