math help

What is 78/10 + 6/9?

What is 78/10 + 6/9?

Here's how you add

78
10
+
6
9

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 9, and get 702, then we multiply 10 by 9 and get 90.

78/10 times 9

Now for the second term. You multiply 6 by 10, and get 60, then multiply 10 by 9 and get 90.

6/9 times 10

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

702
90
+
60
90

Step 2

Since our denominators match, we can add the numerators.

702 + 60 = 762

That gives us the sum, which is

762
90

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:

762
90
÷ 2 =
381
45

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:

381
45
÷ 3 =
127
15

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...

No good. 17 is larger than 15. So we're done reducing.

Congratulations! Here's your final answer to 78/10 + 6/9

78
10
+
6
9
=
127
15
© 2014 Randy Tayler