math help

What is 15/60 + 8/9?

What is 15/60 + 8/9?

Let's add

15
60
+
8
9

Step 1

We can't add two fractions with different denominators (the bottom number). So you need to get a common denominator - both bottom numbers need to match. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 15 by 9, and get 135, then we multiply 60 by 9 and get 540.

15/60 times 9

Do the same for the second term. We multiply 8 by 60, and get 480, then multiply 60 by 9 and get 540.

8/9 times 60

So now our fractions look like this:

135
540
+
480
540

Step 2

Since our denominators match, we can add the numerators.

135 + 480 = 615

Now we have an answer.

615
540

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

To find out, we try dividing it by 2...

No good. So next you try the next prime number, which is 3...

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

615
540
÷ 3 =
205
180

So far so good... let's try to divide by that number again.

No good. So next you try the next prime number, which is 5...

Are both the numerator and the denominator evenly divisible by 5? Yes! So we reduce it:

205
180
÷ 5 =
41
36

So far so good... let's try to divide by that number again.

No good. So next you try the next prime number, which is 7...

No good. So next you try the next prime number, which is 11...

No good. So next you try the next prime number, which is 13...

No good. So next you try the next prime number, which is 17...

No good. So next you try the next prime number, which is 19...

No good. So next you try the next prime number, which is 23...

No good. So next you try the next prime number, which is 29...

No good. So next you try the next prime number, which is 31...

No good. So next you try the next prime number, which is 37...

No good. 37 is larger than 36. So we're done reducing.

And we're done! Here's the final answer to 15/60 + 8/9

15
60
+
8
9
=
41
36
© 2014 Randy Tayler