math help

What is 3/20 + 7/12?

What is 3/20 + 7/12?

Here's how to add

3
20
+
7
12

Step 1

Of course, you can't add two fractions if the denominators (bottom numbers) don't match. To get a common denominator, multiply the denominators together. Then we fix the numerators by multiplying each one by their other term's denominator.

Now you multiply 3 by 12, and get 36, then we multiply 20 by 12 and get 240.

3/20 times 12

Do the same for the second term. We multiply 7 by 20, and get 140, then multiply 20 by 12 and get 240.

7/12 times 20

The problem now has new fractions to add:

36
240
+
140
240

Step 2

Since our denominators match, we can add the numerators.

36 + 140 = 176

This yields the answer

176
240

Step 3

The last step is to reduce the fraction if we can.

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

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

176
240
÷ 2 =
88
120

Let's try dividing by that again...

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

88
120
÷ 2 =
44
60

Let's try dividing by that again...

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

44
60
÷ 2 =
22
30

Let's try dividing by that again...

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

22
30
÷ 2 =
11
15

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 3...

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...

No good. 13 is larger than 11. So we're done reducing.

There you have it! Here's the final answer to 3/20 + 7/12

3
20
+
7
12
=
11
15
© 2014 Randy Tayler