The same numerator or the same denominator.
I am not entirely sure what you mean, but if you need to add, subtract, or compare two fractions, they need to have the same denominator.
You DO need a common denominator to add, subtract, or compare fractions. You DO NOT need a common denominator to multiply or divide fractions.
To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.
Two ways: convert them to decimals or convert them to similar fractions and compare the numerators.
you compare them
You can compare similar fractions by looking at their numerators. You can compare dissimilar fractions by converting them to similar fractions and looking at their numerators. You can convert a dissimilar fraction to a similar fraction by finding the least common denominator.
you have to compare the common fractions
If the fractions have different denominators, you need to: 1) Convert to equivalent fractions with a common denominator, 2) Compare the numerators. If the fractions already have the same denominator, there is no need for the first step - which happens to be the most difficult step. Note that as a shortcut, you don't need the LEAST common denominator, any denominator can do. Thus, you can just use the product of the two denominators as the common denominator. As a result, to compare the fractions, you simply multiply the numerator of each fraction by the denominator of the other one, and then compare. However, this is still more work than simply comparing two numbers.
You can either convert fractions to decimals and compare the decimal numbers; find equivalent fractions with the same denominator and then compare numerators or find equivalent fractions with the same numerator and then compare denominators.
When the numbers are greater than 1
To compare fractions, convert both of them to a common denominator.
Assuming the fractions are "normalized" (the fractional part is less than 1): First compare the integer part. If the integer part is the same, you need to compare the fractions. If the denominator of the fractions is different, you have to convert to a common denominator. The simplest way to find a common denominator is to multiply both denominators (i.e., you don't need the LEAST common denominator - any common denominator will do).