You need to know the least common denominator (LCD) of 4 and 90 if you want to add or subtract two fractions with 4 and 90 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 4 and 90 is 180.
Here is a math problem example where you need to know the LCD of 4 and 90 to solve:
3/4 + 2/90 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
180/4 = 45
180/90 = 2
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 45 = 135
2 x 2 = 4
Step 3) Put it all together to solve the problem:
135/180 + 4/180 = 139/180
= 3/4 + 2/90 = 139/180
It's that easy! Once again, the lowest common denominator (LCD) of 4 and 90 is as follows:
180
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