You need to know the least common denominator (LCD) of 2 and 1 if you want to add or subtract two fractions with 2 and 1 as denominators.
The least common denominator, also called lowest common denominator (LCD), of 2 and 1 is 2.
Here is a math problem example where you need to know the LCD of 2 and 1 to solve:
3/2 + 2/1 = ?
Step 1) Take the LCD and divide each denominator by it as follows:
2/2 = 1
2/1 = 2
Step 2) Multiply each nominator with the respective answers from Step 1:
3 x 1 = 3
2 x 2 = 4
Step 3) Put it all together to solve the problem:
3/2 + 4/2 = 7/2
= 3/2 + 2/1 = 7/2
It's that easy! Once again, the lowest common denominator (LCD) of 2 and 1 is as follows:
2
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