To find the least common denominator, list the multiples of each denominator. The lowest one they have in common is the LCD.
For example:
2/3 and 3/4:
The multiples of 3 are: 3, 6, 9, 12, 15, 18, 24...
The multiples of 4 are: 4, 8, 12, 16, 20, 24...
The common multiples are 12 and 24. Since 12 is the least, it is the LCM.
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Pick two of the fractions and find the Least Common Multiple of those two denominators. Then take that number, and find the Least Common Multiple between that and the third denominator. This number will be the Least Common Denominator between the three fractions.If you don't care to find the Least common denominator, then just take the three denominators, and multiply them together.
Option 1: Find a common denominator for the two fractions. It need not be the least common denominator; for example, for two fractions, if you just multiply the two denominators, you get a common denominator. Convert all the fractions to the common denominator. Then you can compare. Option 2: Convert each fraction to decimal, by dividing the numerator by the denominator. Then you can compare the decimals.
Addition or subtraction of fractions require "like" fractions: that is, fractions with the same denominator.
The least common denominator of fractions is the smallest multiple of the denominators that they both share. To find the least common denominator of 2/3 and 7/12, you need to find the least common multiple of 3 and 12, which is 12. Therefore, the least common denominator of 2/3 and 7/12 is 12.
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.