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 3 years ago
can someone explain to me how to add 5/20 and 6/15 I don't understand lowest common denominators?
 3 years ago
can someone explain to me how to add 5/20 and 6/15 I don't understand lowest common denominators?

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misterf
 3 years ago
Best ResponseYou've already chosen the best response.4A really easy way to do this (although not the most efficient) is to just start listing all the multiples of the denominators:

julie
 3 years ago
Best ResponseYou've already chosen the best response.0Yeah, basically you can't add two fractions unless they have the same denominator.

misterf
 3 years ago
Best ResponseYou've already chosen the best response.4the denoms are 20 and 15, so list the multiples: 15: 15, 30, 45, 60, 75 ... 20: 20, 40, 60, 80 ...

misterf
 3 years ago
Best ResponseYou've already chosen the best response.4here you can move from left to right until you find one that's in both lists :)

albertw
 3 years ago
Best ResponseYou've already chosen the best response.0hmmm, ok, so how would I add them?

julie
 3 years ago
Best ResponseYou've already chosen the best response.0Ok so once you find the common denominator  above, we see that it would be 60.

siddharth
 3 years ago
Best ResponseYou've already chosen the best response.0Well, to add or subtract fractions, you have to make sure the bottom numbers on both fractions are the same. So, the best way to add two fractions with different denominators is to find the Lowest Common Multiple, and change the fractions to that form to perform the addition.

julie
 3 years ago
Best ResponseYou've already chosen the best response.0Then you find how you make the denominators of both the same as that common one. So 15 * 4 = 60 and 20 * 3 = 60.

julie
 3 years ago
Best ResponseYou've already chosen the best response.0Then you multiply the numerator, too: 6 * 4 = 24 15 * 4 = 60 and 5 * 3 = 15 20 * 3 = 60

misterf
 3 years ago
Best ResponseYou've already chosen the best response.4\[\frac{5}{20} = \frac{15}{60}\] \[\frac{6}{15} = \frac{24}{60}\] then add them normally: \[\frac{15}{60} + \frac{24}{60} = \frac{39}{60}\] does this make sense?

julie
 3 years ago
Best ResponseYou've already chosen the best response.0Haha misterf beat me to it :)

misterf
 3 years ago
Best ResponseYou've already chosen the best response.4please gimme a medal if i helped i am collecting them :p

julie
 3 years ago
Best ResponseYou've already chosen the best response.0When you add two fractions and they have the same denominator, the denominator stays the same and you just add the numerators.

siddharth
 3 years ago
Best ResponseYou've already chosen the best response.0Misterf explained it really nicely. Let us know if you don't understand something, albertw. I gave you a medal as well, misterf :)
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