Because when you compare fractions with the same denominators, you do not have to find the least common denominator (LCM or LCD).
The function of the numbers in question. The process is the same. When comparing two whole numbers, we call it the LCM. When comparing two fractions, we call it the LCD.
Only if the problem asks you too
The LCD of two fractions is the same as the LCM of their denominators.
The LCD for fractions is the LCM (least common multiple) of all of the denominators.
LCM can apply to terms which don't look like fractions LCD (denominator) has to be fractions. The LCM of the denominators is the LCD.
The "D" in LCD stands for denominator. The LCD is the same process as the LCM of the denominators.
When reducing fractions to their lowest terms or finding the LCD of fractions
Ordinarily, one finds the least common denominator (LCD) of a set of common fractions in order to add or subtract the set of fractions. The LCD is the least common multiple (LCM) of the denominators of the set of fractions. Without knowing whatis to be multiplied by the LCD, and why, this question is ambiguous.
The LCD, or Lowest Common Denominator, is the smallest multiple of each of the denominators of a set of fractions. So, assuming that 2, 4 and 5 are denominators of fractions (1/2, 1/4 and 1/5, for example), the LCD would be 20, because 20 is the lowest number that 2, 4 and 5 multiply into. So, your new fractions would be 10/20, 5/20 and 4/20. The purpose of finding the LCD is to allow for multiplying fractions together, or simply comparing them easily.
Not true. Try 1/6 + 1/3
Sometimes you won't be able to, but it's usually a good idea.