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Add and Sub Fractions unalike denominators

Added Oct 11, 2015 •

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Learn how to Add and Subtract fractions with unalike denominators

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hi welcome to Math Antics in the last video turn how easy it is to add and subtract fractions that have the same bottom number we called those like fractions but off and you'll be asked to add or subtract fractions that have turn bottom numbers or unlike fractions and we learn that the only way we can do that is to change are fractions so that they do have the same bottom number alright then how do we do that how can we change to unlike fractions into two like fractions how do we get our fractions to have a common denominator the answer is we need to use equivalent fractions you remember what equivalent fractions are right there fractions that have the same value but use different top and bottom warmers like 1 / 2 and 2/4 they both represent 1/2 but with different numbers what whenever we have two unlike fractions that we need to add if we could find a quill fractions to use instead and if those new equivalent fractions had the same bottom numbers as each other then we'd be all set we have to like fractions and atom using our procedure but how do we find equivalent fractions that have a common denominator or the same bottom number well there's two main ways of doing it in this video we're only going to learn the first way of doing it and I like to call this way finding the easiest common denominator in the next video we'll talk about another method some of you may have already heard about it's called finding the least common denominator okay so how does this easiest common denominator method work well even though this is an easy it might sound a little complicated at first but don't worry it'll make a lot more sense once you've seen a few examples in this method the common denominator is always going need the product of the bottom numbers in other words it will be the number you would get if you multiply the bottom numbers together basically all we're going to do is take the two volume numbers and make two different whole fractions using them then we're going to move the whole fractions to the opposite sides and multiply them by are unlike fractions yes we gave us two new equivalent fractions that will have the same bottom number then we can add or subtract them easily okay let's try a couple example so we see this method in action let's add the fractions 2/5 and 1/3 bees are not like fractions because they have different bottom numbers so we're going to and the common denominator will use is the product of the bottom numbers 5 times 3 equals 15 we change them by multiplying each buy a whole fraction the first whole fraction is going to be 3/3 because 3 is the second fractions denominator and the second whole fraction is going read 5/5 because 5 is the first fractions denominator next we multiply starting with our first fraction on the top three times two cool sex and on the bottom three times 5 equals 15 so our first fraction has become 6/15 now for the second fraction stop 1 * 5 equals 5 and on the bottom three times 5 equals 15 so our second fraction has become 5:15 now add the musing are procedure for adding like fractions we had the top numbers 6 + 5 equals 11 and then we keep the same bottom number which is 15 so that what is the answer to 2/5 + 1/3 is 11:15 that's pretty easy huh alright let's see one more example of this method less fractions 7/8 and 3/10 are common denominator for this problem is going to be 80 because that's what we get when we multiply the denominators together 8 times 10 equals 80 will multiply are 7/8 by the whole fraction 10 over 10 and will multiply 3/10 by the whole fraction 8 over 8 then when we do our multiplication the 8 x 10 will give us 80 on the bottom of both fractions for the top of the first fraction we have seven times 10 equal and the top of the second fraction we have three times 8 equals 24 now that we have light fractions we can just add the top numbers 70 24 equals 94 and keep the bottom number the same at so 7 over 8 plus 3 over 10 equals 94 over 80 some of you see that this answer could be simplified be sure to check out our videos on mixed numbers and simplifying fractions to see how you can do that for your final answer alright what's the first way you can find the common denominator and change your unlike fractions into like fractions so you can add or subtract them easily remember practice is really important in math to be sure to do the exercises for this section so you really get the hang of it after that check out the next video and I'll show you how to use a different method to find what we called the least common Terminator thanks for watching and I'll see you next time  learn more at math

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Add and Sub Fractions unalike denominators

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