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  • In this video, were gonna to learn the basics about how to add fractions.

  • Now a lot of math books will teach you how to add fractions before they teach you how to multiply them,

  • but here at Math Antics, we think you should learn the other way around.

  • You remember how easy it is to multiply fractions, right?

  • You just multiply the top numbers together, and you multiply the bottom numbers together, and you have your answer.

  • So, you might be wondering, “Wellcan’t we just do that with addition too?”

  • Can’t we just add the top numbers together and add the bottoms together and get our answer?”

  • Well alright, let’s try it and see…. but I’ve got a bad feeling about this!

  • Let’s try adding 1/2 to 1/2

  • So if we added the top numbers, we’d get 2

  • And if we added the bottom numbers, we’d get 4

  • Butwell that can’t be right!, because 2 over 4 simplifies to one-half.

  • And if you add one-half and one-half, you should get a wholenot a half!

  • [Alarm sound] Uh Oh! We must have broke some sort of math rule! I’m outta here!!

  • Okay, here’s what we did wrong.

  • It turns out that there’s some important math rules calledOrder of Operations

  • that say you have to do multiplication and division BEFORE you do addition and subtraction.

  • Now because fractions are just division problems, if you just added the top numbers and added the bottom numbers,

  • you'd be breaking those rules because you’d be doing the addition before the division.

  • So, what are we gonna do instead?

  • Well fortunately, there’s a trick that lets us work around the Order of Operations rules and add fractions without dividing.

  • But there’s a catch. It only works for fractions that have the same bottom numbers.

  • The trick is, if fractions have the same bottom numbers,

  • we can add them by just adding the top numbers together and keeping the same bottom number in our answer.

  • For example, to add one-half and one-half, we just add the top numbers; and 1 and 1 gives us 2.

  • But we DON’T add the bottom numbers. We just use the same bottom number in the answer, which is 2.

  • So, 2 over 2 is a whole fraction. And that makes sense because if you add one-half and one-half, you get a whole!

  • Let’s see a few more examples. …like this one: 5 over 16 plus 2 over 16.

  • Again, since the bottom numbers are the same, it’s easy to add these fractions.

  • All we do is add the top numbers together: 5 plus 2 equals 7, and that’s the top number of our answer.

  • Then we just keep 16 as the bottom number of our answer.

  • So, 5 over 16, plus 2 over 16, equals 7 over 16. Pretty easy, huh?

  • But what about subtracting fractions? Does that work the same way?

  • Yep, if the bottoms numbers are the same, all you have to do is subtract the top numbers and keep the same bottom number in your answer.

  • Here’s an example of subtracting fractions with the same bottom numbers: 5 over 9 minus 2 over 9.

  • First we subtract the top numbers: 5 minus 2 equals 3.

  • Then we just write the same bottom number in our answer: 9

  • So, 5 over 9, minus 2 over 9, is 3 over 9.

  • Yep, adding and subtracting fractions with the same bottom numbers is easy.

  • And there’s a special name for problems like this. It’s calledAdding or SubtractingLikeFractions.”

  • A teacher once told me that theyre calledlikefractions because the bottom numbers are the same, (oralike’)

  • but I think it’s because they secretly like each other.

  • Just kidding. But seriously, ‘likefractions are easy to add with the trick we just learned,

  • but what happens if you want to add twounlikefractions?

  • What do you do if you have fractions with DIFFERENT bottom numbers?

  • Unfortunately, the only way we can addunlikefractions without doing the division first, is to change them so that they DO have the same bottom numbers.

  • In other words, we need to change ourunlikefractions intolikefractions so we can just use our trick.

  • In math language, that’s calledfinding a common denominator”.

  • Now remember that a ‘denominatoris just a fancy math word for the bottom number of a fraction.

  • Andcommonjust means that theyre the same.

  • So, how do we find a common denominator so that we can add or subtractunlikefractions?

  • That’s what were gonna learn in the next video.

  • But before you move on, be sure to do the exercises for this section.

  • Learn more at www.mathantics.com

In this video, were gonna to learn the basics about how to add fractions.

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数学アンチックス - 分数の足し算と引き算 (Math Antics - Adding and Subtracting Fractions)

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    Yassion Liu に公開 2021 年 01 月 14 日
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