math help

What is 21/33 + 3/7?

What is 21/33 + 3/7?

Let's add

21
33
+
3
7

Step 1

We can't add two fractions with different denominators (the bottom number). So you need to get a common denominator - both bottom numbers need to match. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 21 by 7, and get 147, then we multiply 33 by 7 and get 231.

21/33 times 7

Do the same for the second term. We multiply 3 by 33, and get 99, then multiply 33 by 7 and get 231.

3/7 times 33

So now our fractions look like this:

147
231
+
99
231

Step 2

Since our denominators match, we can add the numerators.

147 + 99 = 246

So the answer is:

246
231

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

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:

246
231
÷ 3 =
82
77

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...

No good. 79 is larger than 77. So we're done reducing.

Congratulations! Here's your final answer to 21/33 + 3/7

21
33
+
3
7
=
82
77
© 2014 Randy Tayler