math help

What is 4/40 + 3/12?

What is 4/40 + 3/12?

This is how we add

4
40
+
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 4 by 12, and get 48, then we multiply 40 by 12 and get 480.

4/40 times 12

Now for the second term. You multiply 3 by 40, and get 120, then multiply 40 by 12 and get 480.

3/12 times 40

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

48
480
+
120
480

Step 2

Since our denominators match, we can add the numerators.

48 + 120 = 168

Answer:

168
480

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:

168
480
÷ 2 =
84
240

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

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

84
240
÷ 2 =
42
120

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

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

42
120
÷ 2 =
21
60

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 3...

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

21
60
÷ 3 =
7
20

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...

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. 11 is larger than 7. So we're done reducing.

And we're done! Here's the final answer to 4/40 + 3/12

4
40
+
3
12
=
7
20
© 2014 Randy Tayler