math help

What is 4/15 + 5/12?

What is 4/15 + 5/12?

Let's add

4
15
+
5
12

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 4 by 12, and get 48, then we multiply 15 by 12 and get 180.

4/15 times 12

Do the same for the second term. We multiply 5 by 15, and get 75, then multiply 15 by 12 and get 180.

5/12 times 15

So now our fractions look like this:

48
180
+
75
180

Step 2

Since our denominators match, we can add the numerators.

48 + 75 = 123

Now we have an answer.

123
180

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...

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 4/15 + 5/12

4
15
+
5
12
=
41
60
© 2014 Randy Tayler