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In order to add and subtract using non-common denominators, you must find a common denominator. The easiest way of finding one is to multiply the two denominators. But there may be a smaller number (least common denominator).
Mutiply the numerator and denominator of the first number by the second denominator (effectively multiplying by 1). Then multiply the numerator and denominator of the second number by the original denominator of the first number. This will leave the denominators the same.
Example : add 1/3 and 1/4
Multiply 1/3 by 4/4 to yield 4/12. Multiply 1/4 by 3/3 to yield 3/12. Add the numerators.
1/3 + 1/4 = 4/12 + 3/12 = 7/12
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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.
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
When you add or subtract fractions with the same denominators what happens to the denominator in your answer?
It stays the same. Only the numerators change.
