Step 1: Finding the Lowest Common Denominator (LCD)
For this instructable we will be using a simple equation 4/5+6/15= x.
Multiples of 5 are 5, 10, 15, 20, 25,...
Multiples of 15 are 15, 30, 45,...
But wait! 15 is a multiple of both 5 and 15!
Our LCD is 15
Step 2: I Found My LCD, Now What?
4/5 * 3/3 = 12/15
for help on multiplying fractions see step 3 of this instructable by meeze
Why can we do this? Wouldn't that change the equation?
If the numerator and the denominator are the same it is equivalent to one (1). As we all know multiplying anything by one causes the number to stay the same.
Step 3: Now You Have the Two Parts of Your Equation Finished. What Now?
a/b + c/b = x
To find out what x equals we add across the numerators and carry our denominator across.
Going back to our example before:
12/15 + 6/15 = 18/15
18/15??? how does that work?
This is called an improper fraction. An improper fraction is one in which the numerator is greater than the denominator.
To simplify an improper fraction we need to find out how many times the denominator goes into the numerator.
18/15, how many times does 15 go into 18?
Now we take this number multiply it by the denominator and subtract it from the numerator.
This will give us a whole number usually followed by a fraction.
we get 1 3/15(one and three-fifteenths)
If we want to put this fraction in simplest form we need to simplify the fraction.
divide the top and bottom by 3
and we get 1/5(one-fifth)
put this back into our answer and our final solution is...
1 1/5(one and one-fifth)
4/5 + 6/15 = 1 1/5
Step 4: But What If You Have More Than Two Fractions to Add???
For a equation with more than two fractions you must find the LCD of all the fractions.
6/5 + 3/6 + 2/15 =x
For this we need to find the LCD of: 5, 6, and 15
6= 6,12,18,24,30, 26,...
15= 15, 30 , 45,...
But wait! 30 is a multiple of 5, 6, and 15!!!
Our LCD is 30
After finding the LCD of all of your fractions you follow steps 2 and 3 the same way.