How do you find the LcD of the fractions with the following denominators: 30, 18, and 15?
To find the LCD, I like to first do a prime factorizations:
The LCD will have all the elements that each of the denominators have.
First we have 2's. Both the 30 and the 18 have a 2, so we put in one:
Next to 3's. The 18 has two of them and so we put in two:
Now to 5's. Both the 30 and the 15 have one, so we put in one:
There are no other primes to include, so we can now multiply it out:
So let's try it out - let's say we're doing:
We want the LCD to be 90: