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How do you add and subtract fractions with different denominators?
Wiki User
∙ 13y ago
You find the least common multiple of the denominators [or least common denominator].
Basically, the Least Common Denominator equals the two denominators multiplied together and then divided by any common prime factors. It is easy to see that the numbers 2 and 3 have a common denominator of 6. But the number 4 and 6 do not have a least common denominator of 24, because both numbers are factors of the number 12 (the least number).
Example : add 1/2 and 1/3 -- multiply the numerator and denominator by the same number : (1/2) x (3/3) = 3/6 and (1/3) x (2/2) = 2/6. We are multiplying them by a fraction equal to 1.
Now you can add 3/6 + 2/6 = 5/6
Example : subtract 1/6 from 3/4 -- multiply 1/6 by 2/2 and multiply 3/4 by 3/3
1/6 = 2/12 and 3/4 = 9/12
so 3/4 - 1/6 equals 9/12 - 2/12 = 7/12
If the result is a reducible fraction, reduce it.
Wiki User
∙ 13y ago
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When you add or subtract fractions with unlike denominators why do you have to find LCM?
Because to add fractions, the denominators must be equal.
How would you add or subtract fractions with like denominators?
The same way you would add or subtract whole numbers, leaving the denominators alone.
When do you need a common denominator?
The denominators must be the same before you can add or subtract fractions.
Why do you need a common denominator?
Common Denominator means that the denominators in two (or more) fractions are common, or the same. The common denominator is important because before you can add or subtract fractions, the fractions need to have a common denominator.Sometimes fractions have different denominators, like 2/3 and 3/4. If you want to add or subtract them, they need to have the same denominator. In order to do that, you find a common denominator which is the same thing as a common multiple, only with denominators.
Can you explain adding and subtracting fractions with like denominators?
When you add or subtract fractions with like denominators, you just add or subtract the numerators and put them over the same denominator. For example, 3/5 - 2/5 = (3 - 2)/5 = 1/5
Why are two fractions converted into like fractions?
Because you can't add or subtract fractions that have different denominators. Making them like fractions, by multiplying so the denominators are the same, you can add and/or subtract them.
How do you add and subtract by fractions?
If the fractions have the same denominator, add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible. If the fractions have different denominators, find the LCM of the denominators and convert the fractions to equivalent fractions with like denominators. Then add and subtract the numerators as if the denominators weren't there and put the result over that denominator. Reduce if possible.
Why does the equivalent fraction make adding and subtracting fractions easier?
You cannot add or subtract fractions with different denominators. If the denominators are different then you need to work with equivalent fractions.
How do you add two fractions that have like denominators?
In fractions, you can NEVER add or subtract
When you add or subtract fractions with unlike denominators why do you have to find LCM?
Because to add fractions, the denominators must be equal.
Why would you want to rename fractions with the LCD?
Possible reasons: To add or subtract fractions, To compare fractions with different denominators.
Why can't you add or subtract fractions that have different denominators?
YOU JUST CANT....go on you try it
How would you add or subtract fractions with like denominators?
The same way you would add or subtract whole numbers, leaving the denominators alone.
What do you not have to think about when you add or subtract fractions?
Whether the denominators are common or not.
How is finding the LCM revelant when adding and subtracting fractions?
To add and subtract fractions, you need common denominators. To find the common denominator, find the LCM of the denominators you wish to add or subtract.
What is least common multiple or LCM?
The LCM is used to help you add or subtract fractions with different denominators.
When or why would it be useful to know the least common multiple of a set of numbers?
When you are trying to add or subtract fractions with different denominators.
