You need to know the least common denominator (LCD) of 7 and 90 if you want to add or subtract two fractions with 7 and 90 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 7 and 90 is 630.
Here is a math problem example where you need to know the LCD of 7 and 90 to solve:
3/7 + 2/90 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
630/7 = 90
630/90 = 7
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 90 = 270
2 x 7 = 14
Step 3) Put it all together to solve the problem:
270/630 + 14/630 = 284/630
= 3/7 + 2/90 = 284/630
It's that easy! Once again, the lowest common denominator (LCD) of 7 and 90 is as follows:
630
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