math help

What is 1/15 + 9/12?

What is 1/15 + 9/12?

This is how you add

1
15
+
9
12

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 1 by 12, and get 12, then we multiply 15 by 12 and get 180.

1/15 times 12

Now for the second term. You multiply 9 by 15, and get 135, then multiply 15 by 12 and get 180.

9/12 times 15

This gives us a new problem that looks like so:

12
180
+
135
180

Step 2

Since our denominators match, we can add the numerators.

12 + 135 = 147

So what's the answer so far?

147
180

Step 3

Can this fraction be reduced?

First, we attempt to divide 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:

147
180
÷ 3 =
49
60

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 49. So we're done reducing.

Congratulations! Here's your final answer to 1/15 + 9/12

1
15
+
9
12
=
49
60
© 2014 Randy Tayler