You need to know the least common denominator (LCD) of 5 and 18 if you want to add or subtract two fractions with 5 and 18 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 5 and 18 is 90.
Here is a math problem example where you need to know the LCD of 5 and 18 to solve:
3/5 + 2/18 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
90/5 = 18
90/18 = 5
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 18 = 54
2 x 5 = 10
Step 3) Put it all together to solve the problem:
54/90 + 10/90 = 64/90
= 3/5 + 2/18 = 64/90
It's that easy! Once again, the lowest common denominator (LCD) of 5 and 18 is as follows:
90
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