What is 21/63 + 7/12?

Here's how you add

Step 1

Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term.

So, we multiply 21 by 12, and get 252, then we multiply 63 by 12 and get 756.

Now for the second term. You multiply 7 by 63, and get 441, then multiply 63 by 12 and get 756.

We now have a new problem, that looks like this:

Step 2

Since our denominators match, we can add the numerators.

252 + 441 = 693

That gives us the sum, which is

Step 3

Now, do we need to simplify this fraction?

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:

Now, try the same number again.

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

Now, try the same number again.

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

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

Are both the numerator and the denominator evenly divisible by 7? Yes! So we reduce it:

Now, try the same number again.

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

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

No good. 13 is larger than 11. So we're done reducing.

Congratulations! Here's your final answer to 21/63 + 7/12