 # What is 5/10 + 2/9? 5 10
+
 2 9

## Step 1

Of course, you can't add two fractions if the denominators (bottom numbers) don't match. To get a common denominator, multiply the denominators together. Then we fix the numerators by multiplying each one by their other term's denominator.

Now you multiply 5 by 9, and get 45, then we multiply 10 by 9 and get 90. Do the same for the second term. We multiply 2 by 10, and get 20, then multiply 10 by 9 and get 90. The problem now has new fractions to add:

 45 90
+
 20 90

## Step 2

Since our denominators match, we can add the numerators.

45 + 20 = 65

 65 90

## Step 3

The last step is to reduce the fraction if we can.

To find out, we try dividing it by 2...

No good. So next you try the next prime number, which is 3...

No good. So next you try the next prime number, which is 5...

Are both the numerator and the denominator evenly divisible by 5? Yes! So we reduce it:

 65 90
÷ 5 =
 13 18

So far so good... let's try to divide by that number again.

No good. So next you try the next prime number, which is 7...

No good. So next you try the next prime number, which is 11...

No good. So next you try the next prime number, which is 13...

No good. So next you try the next prime number, which is 17...

No good. 17 is larger than 13. So we're done reducing.

And we're done! Here's the final answer to 5/10 + 2/9

 5 10
+
 2 9
=
 13 18