Adding, Subtracting, Multiplying & Dividing Fractions

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Fractions can be added, subtracted, multiplied and divided the same way whole numbers can. Learn about adding, subtracting, multiplying and dividing fractions with help from a mathematics educator in this free video clip.

Part of the Video Series: Mathematics Equations & More
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Hi, my name is Jimmy Chang and we're here to discuss adding, subtracting, multiplying, and dividing fractions. Now with adding and subtracting it works a little bit differently than with multiplying and dividing so we're going to talk about them in kind of two groups. Now with adding and subtracting fractions the one thing that you really want to keep in mind is to make it work, to even add or subtract fractions you really have to take into account the least common denominator. So for example if you have 1/2-1/4, we're using subtraction as an example but adding works the same way. You really can't subtract the two fractions unless you have the least common denominator. In other words you have to take a look at what's the least common denominator of 2 and 4. In other words what number will both go into both 2 and 4 and that will be the number 4. So what you've got to think about is convert both the 1/2 and the 1/4 and the least common denominator is going to be 4. Now the second term will not change but the first one will. And to get 4 you have to multiply both the top and bottom by 2. So it's really 2/4-1/4 which is of course 1/4. Now again, with adding and subtracting you really have to take into account the LCD, or least common denominator. But when it comes to multiplying and dividing you don't really have to worry about that. With multiplication if you have 1/3x2/7 for example you can actually multiply across without having to worry about the least common denominator. So this will be 1x2 which is 2 and 3x7 which is going to give you 21. So 1/3x2/7 is going to give you 2/21. Now if you were to divide, lets just say you have 2/5 divided by 1/2. Dividing fractions is the same thing as multiplying except that you have to think about the reciprocal of the 2nd fraction so for example if you're dividing by 1/2 you have to take a look the 1/2 and think about its reciprocal. So 2/5 x the reciprocal of 1/2 is 2/1 so it would be two over 1 and just like with multiplication you just have to multiply across. 2 x 2 is 4 and 5 x 1 is 5. So when you're dividing 2/5 by 1/2 you get 4/5. So I'm Jimmy Chang and those are a few tips on adding, subtracting, multiplying, and dividing fractions.

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