 # What is 9/12 + 4/8? Here's how you add

 9 12
+
 4 8

## Step 1

We still have different denominators (bottom numbers), though, so we need to get a common denominator. This will make the bottom numbers match. Multiply the denominators together first. Now, multiply each numerator by the other term's denominator.

Now we multiply 9 by 8, and get 72, then we multiply 12 by 8 and get 96. Now for the second term. You multiply 4 by 12, and get 48, then multiply 12 by 8 and get 96. This gives us a new problem that looks like so:

 72 96
+
 48 96

## Step 2

Since our denominators match, we can add the numerators.

72 + 48 = 120

That gives us an answer of

 120 96

## Step 3

Can this fraction be reduced?

First, we attempt to divide it by 2...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

 120 96
÷ 2 =
 60 48

Let's try dividing by that again...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

 60 48
÷ 2 =
 30 24

Let's try dividing by that again...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

 30 24
÷ 2 =
 15 12

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 3...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

 15 12
÷ 3 =
 5 4

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 5...

No good. 5 is larger than 4. So we're done reducing.

There you have it! Here's the final answer to 9/12 + 4/8

 9 12
+
 4 8
=
 5 4
© 2014 Randy Tayler