math help

What is 15/60 + 7/9?

What is 15/60 + 7/9?

Here's how to add

15
60
+
7
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 15 by 9, and get 135, then we multiply 60 by 9 and get 540.

15/60 times 9

Now for the second term. You multiply 7 by 60, and get 420, then multiply 60 by 9 and get 540.

7/9 times 60

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

135
540
+
420
540

Step 2

Since our denominators match, we can add the numerators.

135 + 420 = 555

Answer:

555
540

Step 3

Now, do we need to simplify this fraction?

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

Nope. Try the next prime number, 3...

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

555
540
÷ 3 =
185
180

Now, try the same number again.

Nope. Try the next prime number, 5...

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

185
180
÷ 5 =
37
36

Now, try the same number again.

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...

Nope. Try the next prime number, 29...

Nope. Try the next prime number, 31...

Nope. Try the next prime number, 37...

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

Congratulations! Here's your final answer to 15/60 + 7/9

15
60
+
7
9
=
37
36
© 2014 Randy Tayler