math help

What is 12/13 + 9/12?

What is 12/13 + 9/12?

Here's how we add

12
13
+
9
12

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 12 by 12, and get 144, then we multiply 13 by 12 and get 156.

12/13 times 12

Do the same for the second term. We multiply 9 by 13, and get 117, then multiply 13 by 12 and get 156.

9/12 times 13

The problem now has new fractions to add:

144
156
+
117
156

Step 2

Since our denominators match, we can add the numerators.

144 + 117 = 261

The sum we get is

261
156

Step 3

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

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:

261
156
÷ 3 =
87
52

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...

Nope. Try the next prime number, 43...

Nope. Try the next prime number, 47...

Nope. Try the next prime number, 53...

No good. 53 is larger than 52. So we're done reducing.

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

12
13
+
9
12
=
87
52
© 2014 Randy Tayler