math help

What is 25/15 + 3/12?

What is 25/15 + 3/12?

This is how to add

25
15
+
3
12

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 25 by 12, and get 300, then we multiply 15 by 12 and get 180.

25/15 times 12

Now for the second term. You multiply 3 by 15, and get 45, then multiply 15 by 12 and get 180.

3/12 times 15

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

300
180
+
45
180

Step 2

Since our denominators match, we can add the numerators.

300 + 45 = 345

That gives us the sum, which is

345
180

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:

345
180
÷ 3 =
115
60

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:

115
60
÷ 5 =
23
12

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...

No good. 13 is larger than 12. So we're done reducing.

Congratulations! Here's your final answer to 25/15 + 3/12

25
15
+
3
12
=
23
12
© 2014 Randy Tayler