Example of Least Common Denominator:

Example:

Add 1/7 +2 /3 + 11/12 + 4/6

Solution:

Step 1:            Find out primes of each denominator.

7 = 7 (already is a prime number)

3 = 3 (already is a prime number)

12 = 2 x 6 = 2 x 2 x 3

6 = 2 x 3

Step 2:            12 is the largest, so begin with

2 x 2 x 3

Comparing this list to another list, the denominators of 3, 12, and 6 could all be calculated from the list, but 7 cannot be, so a 7 must be involved in the list.

2 x 2 x 3 x 7 = 84

Step 3:            Rewrite the equation

1/7 . 12/12 + 2/3 . 28/ 28 + 11/ 12 . 7/7 +  4/6 . 14/14 =

Step 4: Add

12/84 + 56/84 + 77/84 + 56/84 = 201 /84