math help

What is 7/9 + 9/12?

What is 7/9 + 9/12?

This is how you add

7
9
 +
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 7 by 12, and get 84, then we multiply 9 by 12 and get 108.

7/9 times 12

Now for the second term. You multiply 9 by 9, and get 81, then multiply 9 by 12 and get 108.

9/12 times 9

This gives us a new problem that looks like so:

84
108
 +
81
108

Step 2

Since our denominators match, we can add the numerators.

84 + 81 = 165

So what's the answer so far?

165
108

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:

165
108
 ÷ 3 =
55
36

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...

No good. 37 is larger than 36. So we're done reducing.

Congratulations! Here's your final answer to 7/9 + 9/12

7
9
 +
9
12
 =
55
36
© 2014 Randy Tayler

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