math help

What is 21/33 + 4/12?

What is 21/33 + 4/12?

Here's how to add

21
33
+
4
12

Step 1

Of course, you can't add two fractions if the denominators (bottom numbers) don't match. To get a common denominator, multiply the denominators together. Then we fix the numerators by multiplying each one by their other term's denominator.

Now you multiply 21 by 12, and get 252, then we multiply 33 by 12 and get 396.

21/33 times 12

Do the same for the second term. We multiply 4 by 33, and get 132, then multiply 33 by 12 and get 396.

4/12 times 33

The problem now has new fractions to add:

252
396
+
132
396

Step 2

Since our denominators match, we can add the numerators.

252 + 132 = 384

The sum we get is

384
396

Step 3

The last step is to reduce the fraction if we can.

To find out, we try dividing it by 2...

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

384
396
÷ 2 =
192
198

Now, try the same number again.

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

192
198
÷ 2 =
96
99

Now, try the same number again.

Nope. Try the next prime number, 3...

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

96
99
÷ 3 =
32
33

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 32. So we're done reducing.

Congratulations! Here's your final answer to 21/33 + 4/12

21
33
+
4
12
=
32
33
© 2014 Randy Tayler