Subtracting Mixed Numbers With Regrouping

Video Transcript

"Alright, so you've done a lot of work fractions by now, especially on the addition and subtraction front. But how do you subtract mix numbers with the regrouping. I'm Jimmy and I'm here to answer that question right now. When you have fractions, it's hard enough to subtract them and you've already got the ideas to how to subtract one fraction from another without having to borrow. But there are going to be times which you'll be asked to do that because sometimes you're going to have a smaller fraction subtracted by a larger fraction. So here's an example as to how to do that. You have 10 and 2/7 - 6 and 4/7. You don't want to do the 10 - 6 first even though you re-left to right. You have to deal with the fractions first, the two 2/7 and the 4/7. Now unfortunately, this 4/7 is larger than the 2/7, so you can't subtract 2/7 - 4/7. So what you have to do, whenever the top fraction portion is smaller, you have to regroup or you have to borrow. So, where you borrow from? It has to be from the ten because it's right next to it. If you borrow, two things happen. If you have to borrow 1 whole, the 10 now becomes a 9 because you're borrowing 1 whole. Now this is where the denominator comes in. Because the denominator is 7, that's how many additional pieces you're going to have. So that means that 2 which the numerator up here, now adds 7 extra pieces to help you. So now the 10 and 2/7 become 9 and our new numerator is 9/7. It now has enough pieces to be able to subtract the second fraction. You notice I'm not touching the second fraction, I'm only dealing with the first. But I'm just going to carry over the -6 and 4/7 and now I can subtract both pieces. 9/7 - 4/7, 9 - 4 is 5/7. And now and only now, can I subtract the whole numbers; 9-6 is 3. So therefore, 10 and 2/7 - 6 and 4/7 is 3 and 5/7. So I'm Jimmy and that's how you subtract mix numbers with regrouping."