math help

What is 12/13 + 6/9?

What is 12/13 + 6/9?

Here's how you add

12
13
+
6
9

Step 1

We can't add two fractions with different denominators (the bottom number). So you need to get a common denominator - both bottom numbers need to match. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 12 by 9, and get 108, then we multiply 13 by 9 and get 117.

12/13 times 9

Do the same for the second term. We multiply 6 by 13, and get 78, then multiply 13 by 9 and get 117.

6/9 times 13

So now our fractions look like this:

108
117
+
78
117

Step 2

Since our denominators match, we can add the numerators.

108 + 78 = 186

So the answer is:

186
117

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

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

Nope. Try the next prime number, 3...

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

186
117
÷ 3 =
62
39

Now, try the same number again.

Nope. Try the next prime number, 5...

Nope. Try the next prime number, 7...

Nope. Try the next prime number, 11...

Nope. Try the next prime number, 13...

Nope. Try the next prime number, 17...

Nope. Try the next prime number, 19...

Nope. Try the next prime number, 23...

Nope. Try the next prime number, 29...

Nope. Try the next prime number, 31...

Nope. Try the next prime number, 37...

Nope. Try the next prime number, 41...

No good. 41 is larger than 39. So we're done reducing.

Congratulations! Here's your final answer to 12/13 + 6/9

12
13
+
6
9
=
62
39
© 2014 Randy Tayler