What is 21/63 + 5/12?

This is how we add

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

Now for the second term. You multiply 5 by 63, and get 315, then multiply 63 by 12 and get 756.

This gives us a new problem that looks like so:

Step 2

Since our denominators match, we can add the numerators.

252 + 315 = 567

So what's the answer so far?

Step 3

Can this fraction be reduced?

First, we attempt to divide it by 2...

No good. So next you try the next prime number, which is 3...

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

So far so good... let's try to divide by that number again.

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

So far so good... let's try to divide by that number again.

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

So far so good... let's try to divide by that number again.

No good. So next you try the next prime number, which is 5...

No good. So next you try the next prime number, which is 7...

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

So far so good... let's try to divide by that number again.

No good. 7 is larger than 3. So we're done reducing.

And we're done! Here's the final answer to 21/63 + 5/12