 # What is 8/10 + 7/8? Here's how you add

 8 10
+
 7 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 8 by 8, and get 64, then we multiply 10 by 8 and get 80. Now for the second term. You multiply 7 by 10, and get 70, then multiply 10 by 8 and get 80. This gives us a new problem that looks like so:

 64 80
+
 70 80

## Step 2

Since our denominators match, we can add the numerators.

64 + 70 = 134

That gives us an answer of

 134 80

## 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:

 134 80
÷ 2 =
 67 40

Let's try dividing by that again...

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

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

Nope! So now we try the next greatest prime number, 7...

Nope! So now we try the next greatest prime number, 11...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

Nope! So now we try the next greatest prime number, 29...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

Nope! So now we try the next greatest prime number, 41...

No good. 41 is larger than 40. So we're done reducing.

There you have it! Here's the final answer to 8/10 + 7/8

 8 10
+
 7 8
=
 67 40
© 2014 Randy Tayler