math help

What is 72/63 + 3/12?

What is 72/63 + 3/12?

This is how we add

72
63
+
3
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 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 3 by 63, and get 189, then multiply 63 by 12 and get 756.

3/12 times 63

The problem now has new fractions to add:

864
756
+
189
756

Step 2

Since our denominators match, we can add the numerators.

864 + 189 = 1053

The sum we get is

1053
756

Step 3

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

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:

1053
756
÷ 3 =
351
252

Let's try dividing by that again...

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

351
252
÷ 3 =
117
84

Let's try dividing by that again...

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

117
84
÷ 3 =
39
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 + 3/12

72
63
+
3
12
=
39
28
© 2014 Randy Tayler