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You cannot add fractions with different denominators because they do not represent the same size parts of a whole. (A half is larger than a third, so you cannot add them together as equals until they are expressed with the same denominator.)

When fractions have like denominators, we add the numerators and place them over the denominator, for example:

2/7 + 3/7 = (2 + 3)/7 = 5/7

We can add fractions with unlike denominators by finding their "least common denominator". For example: 2/3 + 5/6 can both be expressed in terms of a least common denominator (6). Multiply the numerator and denominator by the same number to convert the fraction.

2/3 + 5/6 -- multiply the numerator and denominator of 2/3 by 2, and 2/3 = 4/6

4/6 + 5/6 = 9/6 or 11/2

Another example : a common denominator for 3/4 and 1/5 would be 20

and 3/4 = 15/20 [ (3 x 5)/(4 x 5) ]

while 1/5 = 4/20 [ (1 x 4)/(5 x 4)

So 3/4 plus 4/5 would become 15/20 + 4/20 = 19/20.

Q: Why can't you add fractions with unlike denominators?

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If the denominators are not the same, then you have to use equivalent fractions which do have a common denominator . To do this, you need to find the least common multiple (LCM) of the two denominators. To add fractions with unlike denominators, rename the fractions with a common denominator.

YOU JUST CANT....go on you try it

-- Find a common denominator. (It will be a number of which all three denominators are factors. The best choice is their least common multiple.) -- Change the fractions to their equivalents with the common denominator. -- Then add their numerators to get the numerator of their sum.

No.

convert at least one of them so that they have the same denominator, then proceed with the addition or subtraction

Related questions

Because to add fractions, the denominators must be equal.

If the denominators are not the same, then you have to use equivalent fractions which do have a common denominator . To do this, you need to find the least common multiple (LCM) of the two denominators. To add fractions with unlike denominators, rename the fractions with a common denominator. Then add and simplify.

If the denominators are not the same, then you have to use equivalent fractions which do have a common denominator . To do this, you need to find the least common multiple (LCM) of the two denominators. To add fractions with unlike denominators, rename the fractions with a common denominator. Then add and simplify.

If the denominators are not the same, then you have to use equivalent fractions which do have a common denominator . To do this, you need to find the least common multiple (LCM) of the two denominators. To add fractions with unlike denominators, rename the fractions with a common denominator.

because they are the same number

You can totally add fractions with unlike denominators. You have to first find the LCD (least common denominator) to make them the same denomintars. And then you can just simply add them. What you cannot do is add fractions with unlike denominators without changing them to fractions with like denominators. The reason being that you would be attempting to add fractions that are different sizes. 1/2 is not the same size as 1/3, so it would be like trying to add apples and oranges. You have to change them to a common size and that is the reason you have to find the least common denominator first. While you cannot add 1/2 and 1/3, you can add 3/6 and 2/6.

YOU JUST CANT....go on you try it

When adding unlike fractions, find the LCM of the denominators and convert them to it.

The question is based on a complete misunderstanding of what is required. Unlike denominators are NOT required!

No.

-- Find a common denominator. (It will be a number of which all three denominators are factors. The best choice is their least common multiple.) -- Change the fractions to their equivalents with the common denominator. -- Then add their numerators to get the numerator of their sum.

It will enable you to add and subtract fractions with unlike denominators.