Find the LCM of the denominators. For example, we have, [tex] \frac{5}{6}[/tex] and [tex] \frac{6}{7} [/tex]
We need to find the LCM of the denominators, which are 6 and 7. To get LCM, list the prime factors of the numbers.
6 = 2 × 3
7 = 7
Then, just multiply the prime numbers, but not all (you'll understand better in the next example. ☺).
2 × 3 × 7 = 42
Therefore, the LCD/LCM in my example is 42.
Another example. [tex] \frac{25}{30} [/tex] and [tex] \frac{35}{45} [/tex]
30 = 2 × 3 × 5
45 = 3 × 3 × 5
Multiply. 30 & 45 have common prime factor, which is 3 and 5, just multiply the numbers once. (The numbers are bold)
2 × 3 × 3 × 5 = 90
Therefore, the LCM/LCD in my example is 90.
I hope that you'll understand it even if I haven't explained it well. ☺
