Question 149834: When subtracting fraction with different denominator. How do you get the to be the same?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! When subtracting fraction with different denominator. How do you get them to be the same?
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You can always multiply them. For example, x/3 - y/7. 3*7 = 21.
Multiplying will not always give you the LCD, the Least Common Denominator, but it will always work.
Eg, x/6 - y/15. If you multiply 6*15, you get 90, which will work, and you can always reduce the result anyway. However, some problems will ask for the LCD, so you have to know how to get that. If the 2 DENs have common factors, they need to be included only once. In the case of x/6 - y/15, both DENs have a 3, so only one 3 is needed, and the LCD is 30, not 90.
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