math help

What is 21/33 + 7/9?

What is 21/33 + 7/9?

Here's how to add

21
33
+
7
9

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 9, and get 189, then we multiply 33 by 9 and get 297.

21/33 times 9

Do the same for the second term. We multiply 7 by 33, and get 231, then multiply 33 by 9 and get 297.

7/9 times 33

The problem now has new fractions to add:

189
297
+
231
297

Step 2

Since our denominators match, we can add the numerators.

189 + 231 = 420

The sum we get is

420
297

Step 3

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

To find out, we try dividing 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:

420
297
÷ 3 =
140
99

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...

Nope. Try the next prime number, 41...

Nope. Try the next prime number, 43...

Nope. Try the next prime number, 47...

Nope. Try the next prime number, 53...

Nope. Try the next prime number, 59...

Nope. Try the next prime number, 61...

Nope. Try the next prime number, 67...

Nope. Try the next prime number, 71...

Nope. Try the next prime number, 73...

Nope. Try the next prime number, 79...

Nope. Try the next prime number, 83...

Nope. Try the next prime number, 89...

Nope. Try the next prime number, 97...

Nope. Try the next prime number, 101...

No good. 101 is larger than 99. So we're done reducing.

Congratulations! Here's your final answer to 21/33 + 7/9

21
33
+
7
9
=
140
99
© 2014 Randy Tayler