You need to know the least common denominator (LCD) of 2 and 9 if you want to add or subtract two fractions with 2 and 9 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 2 and 9 is 18.
Here is a math problem example where you need to know the LCD of 2 and 9 to solve:
3/2 + 2/9 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
18/2 = 9
18/9 = 2
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 9 = 27
2 x 2 = 4
Step 3) Put it all together to solve the problem:
27/18 + 4/18 = 31/18
= 3/2 + 2/9 = 31/18
It's that easy! Once again, the lowest common denominator (LCD) of 2 and 9 is as follows:
18
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