Question

what is the common denominator for 1/2 and 1/4

Answer 1

4 you multiply 2 times two to get four as your denominator so it would be 2/4 &1/4

Answer 2

Hi there, 

Common denominator indicates that both denominators (2 and 4) 

Would have a common number when they are factored. 

the factors of 2 are : 1 , 2 , 4 , 6
The factors of 4 are : 1 , 2,  4

Since they asked for a common denominator (in which you can transform one of the denominators into the other's by multiplying it by a specific number)
Then the common denominator would be 4

If you are confused let me know, i can provide you with explanation.