math help

What is 78/10 + 2/9?

What is 78/10 + 2/9?

Let's add

78
10
+
2
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 2 by 10, and get 20, then multiply 10 by 9 and get 90.

2/9 times 10

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

702
90
+
20
90

Step 2

Since our denominators match, we can add the numerators.

702 + 20 = 722

Answer:

722
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:

722
90
÷ 2 =
361
45

Let's try dividing by that again...

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

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...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

Nope! So now we try the next greatest prime number, 41...

Nope! So now we try the next greatest prime number, 43...

Nope! So now we try the next greatest prime number, 47...

No good. 47 is larger than 45. So we're done reducing.

There you have it! Here's the final answer to 78/10 + 2/9

78
10
+
2
9
=
361
45
© 2014 Randy Tayler