What is 21/63 + 3/10?

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 10, and get 210, then we multiply 63 by 10 and get 630.

Now for the second term. You multiply 3 by 63, and get 189, then multiply 63 by 10 and get 630.

This gives us a new problem that looks like so:

Step 2

Since our denominators match, we can add the numerators.

210 + 189 = 399

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...

No good. 23 is larger than 19. So we're done reducing.

Congratulations! Here's your final answer to 21/63 + 3/10