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## How can i find a common denominator for a pair of fractions

4/10 and 1/5

the common denominator is 10. because if you were to add 4/10+1/5 you would put:
4/10 + 1/5 and to make the denominator equal to 10 you multiply the top and the bottom by 2 and it would end up looking like this 2/10. therefore your problem would look like this 4/10 +2/10= 6/10. did this help?

To find the lowest common denominator, LCD, you can do three things.
FIRST...
You can observe that 4/10 can be converted into 2/5---both the numerator and denominator, also known as the divisor, can be cut in half.
The numbers are now 2/5 and 1/5.
The lowest common denominator is 5.
SECOND...
Let's just say that this is 1/10 and 1/5.
Neither denominator can be cut.
You can observe that the denominator of the first is twice the denominator of the second.  Therefore, you can take the second number and multiply it by 2/2...
(1/5)(2/2)=2/10
The lowest common denominator is 10.
THIRD...
Let's just say that this is 1/5 and 1/3.
Neither denominator can be cut.
Neither denominator is a multiple of the other.
You can take the denominators of each and multiply these together.
(5)(3)=15
The lowest common denominator is 15.