How can you find the missing numerator with the same denominator?

Answer 1

I assume you want to convert two fractions to a common denominator. Let's see an example. You want to add, subtract, or compare 1/4 and 5/6. The least common denominator is 12 - I assume you already know how to find that. It need not be the least common denominator; any common denominator - for example, the product of the two denominators - will work.

However, let's assume you want to convert to twelfths. To convert the fractions to twelfths, you do the following. To convert 1/4 to ?/12, note that the number 4 must be multiplied by 3 to get 12. In that case, the numerator, 1, must also be multiplied by 3. Thus, you get 3/12. Similarly, to convert 5/6 to ?/12, you need to multiply the bottom (and therefore also the top) by 2, so you get 10/12.