math help

What is 7/20 + 3/9?

What is 7/20 + 3/9?

Here's how we add

7
20
+
3
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 7 by 9, and get 63, then we multiply 20 by 9 and get 180.

7/20 times 9

Now for the second term. You multiply 3 by 20, and get 60, then multiply 20 by 9 and get 180.

3/9 times 20

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

63
180
+
60
180

Step 2

Since our denominators match, we can add the numerators.

63 + 60 = 123

That gives us the sum, which is

123
180

Step 3

Now, do we need to simplify this fraction?

First, we attempt to divide 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:

123
180
÷ 3 =
41
60

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...

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...

No good. 43 is larger than 41. So we're done reducing.

There you have it! Here's the final answer to 7/20 + 3/9

7
20
+
3
9
=
41
60
© 2014 Randy Tayler