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Comparing with multiplication

Sal represents multiplication equations as comparisons.

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Video transcript

- [Instructor] This here is a screenshot from this exercise on Khan Academy. It says, the number 48 is six times as many as eight. Write this comparison as a multiplication equation. So, pause this video and see if you can have a go at that. All right, so, it sounds very fancy. This comparison as a multiplication equation. But really they're just asking us to write this as an equation. And if we were on Khan Academy we would type it in here but I'm just going to do it, this is a screenshot, so I'm just going to do it by digital pen. So, they're saying the number 48, the number 48, and when they say is, another way of interpreting is to say, hey, that's equal to something. Now, what does that equal to? That's equal to six times as many as eight. Well, what's another way to write six times as many as eight? Well, we can write that as six times eight. So this right over here, this is that comparison written as a multiplication equation. That's all they're asking for. And so you would type that in right over there. Let's do another example. Here, we are told, or we are asked, what statement represents the equation seven times four is equal to 28? So, pause this video and think about which choice would you pick. So, let's see. Choice A says, 28 is seven more than four. First of all, that's not true. 28 is not seven more than four. But if you were to write this comparison as an equation, this would be that 28 is, so is equal to seven more than four is seven plus four. Not only is that not true, but that's not the original equation. So we rule that out. 28 is seven times as many as four. Well, this is interesting. 28, 28 is, is equal to seven times as many as four, seven times four. Well, the only difference between this and this is just we've swapped the sides on the equality, which is completely okay. So, 28 is equal to seven times four, that's the same equation, really, as seven times four is equal to 28. So I like this choice. Now let's just look at the other choices. Seven is four times as many as 28. That plays with your head a little bit, but let's just write it as an equation. Seven is so that would be equal to four times as many as 28 that would be four times 28. One, this is not true. Four times 28 is over a 100, so it's not seven. But this is also very different than what we see up here, so we'd rule that out. Seven is four less than 28. Well, this equation would be seven is, so is equal to, four less than 28, so four less than 28 would be 28 minus four. Once again, not only is this not true, 28 minus four is 24, not seven, but this is not that original equation. So we'd rule that one out as well. So we like our choice B.