What is 21/63 + 5/8?

This is how to 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 8, and get 168, then we multiply 63 by 8 and get 504.

Now for the second term. You multiply 5 by 63, and get 315, then multiply 63 by 8 and get 504.

This gives us a new problem that looks like so:

Step 2

Since our denominators match, we can add the numerators.

168 + 315 = 483

That gives us an answer of

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:

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...

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...

No good. 29 is larger than 23. So we're done reducing.

Congratulations! Here's your final answer to 21/63 + 5/8