math help

What is 78/10 + 3/12?

What is 78/10 + 3/12?

Here's how you add

78
10
+
3
12

Step 1

Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term.

So, we multiply 78 by 12, and get 936, then we multiply 10 by 12 and get 120.

78/10 times 12

Now for the second term. You multiply 3 by 10, and get 30, then multiply 10 by 12 and get 120.

3/12 times 10

We now have a new problem, that looks like this:

936
120
+
30
120

Step 2

Since our denominators match, we can add the numerators.

936 + 30 = 966

That gives us the sum, which is

966
120

Step 3

Now, do we need to simplify this fraction?

First, we attempt to divide it by 2...

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

966
120
÷ 2 =
483
60

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:

483
60
÷ 3 =
161
20

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...

No good. 23 is larger than 20. So we're done reducing.

Congratulations! Here's your final answer to 78/10 + 3/12

78
10
+
3
12
=
161
20
© 2014 Randy Tayler