You need to know the least common denominator (LCD) of 12 and 9 if you want to add or subtract two fractions with 12 and 9 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 12 and 9 is 36.
Here is a math problem example where you need to know the LCD of 12 and 9 to solve:
3/12 + 2/9 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
36/12 = 3
36/9 = 4
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 3 = 9
2 x 4 = 8
Step 3) Put it all together to solve the problem:
9/36 + 8/36 = 17/36
= 3/12 + 2/9 = 17/36
It's that easy! Once again, the lowest common denominator (LCD) of 12 and 9 is as follows:
36
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