math help

What is 72/63 + 9/12?

What is 72/63 + 9/12?

This is how you add

72
63
+
9
12

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 72 by 12, and get 864, then we multiply 63 by 12 and get 756.

72/63 times 12

Do the same for the second term. We multiply 9 by 63, and get 567, then multiply 63 by 12 and get 756.

9/12 times 63

So now our fractions look like this:

864
756
+
567
756

Step 2

Since our denominators match, we can add the numerators.

864 + 567 = 1431

Now we have an answer.

1431
756

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! So now we try the next greatest prime number, 3...

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

1431
756
÷ 3 =
477
252

Let's try dividing by that again...

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

477
252
÷ 3 =
159
84

Let's try dividing by that again...

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

159
84
÷ 3 =
53
28

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 5...

Nope! So now we try the next greatest prime number, 7...

Nope! So now we try the next greatest prime number, 11...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

Nope! So now we try the next greatest prime number, 29...

No good. 29 is larger than 28. So we're done reducing.

There you have it! Here's the final answer to 72/63 + 9/12

72
63
+
9
12
=
53
28
© 2014 Randy Tayler