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Multiplying fractions by whole numbers on a number line

Sal multipiies fractions by whole numbers using the number line.

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Video transcript

We're asked to move the orange dot to the number that equals five times 1/3. Alright, so one way to think about it, we just have to move 1/3 five times. So let's do it once, so that's going to be 1/3, you do it twice, you get to 2/3, you do it three times, you get to 3/3, four times, you get to 4/3, five times, you get to 5/3. Five times 1/3 is gonna be 5/3. Or you could say five 1/3, which is the same thing as 5/3, hopefully that makes some sense. Let's do some more examples here. So let's say we need to figure out, so let's see, it says move the orange dot to the number that equals two times 4/3. Alright, so one times 4/3 is just gonna get us to 4/3, and then if we have another 4/3, we're gonna add 4/3 to that, so we're gonna move another 4/3 to the right. So 4/3 plus 4/3 would get us to 8/3. 8/3, I'm having trouble moving this, 8/3. So one times 4/3 is just 4/3, and then two times 4/3 is 8/3. And notice that's the same thing as two times four, which is eight, over three, 8/3. Let's do one more of these. So, move the orange dot to the number that equals three times 3/2. So this is gonna be 0/2, that's just zero, so you could do that a zero times 3/2. One times 3/2, well that will just get us to 3/2. Two times 3/2, we'll add another 3/2, so that'll get us to 6/2. And then three times 3/2, we'll add another 3/2, that gets us to 9/2, and we're done.