math help

What is 3/20 + 11/12?

What is 3/20 + 11/12?

Here's how we add

3
20
+
11
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 11 by 20, and get 220, then multiply 20 by 12 and get 240.

11/12 times 20

The problem now has new fractions to add:

36
240
+
220
240

Step 2

Since our denominators match, we can add the numerators.

36 + 220 = 256

The sum we get is

256
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:

256
240
÷ 2 =
128
120

Now, try the same number again.

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

128
120
÷ 2 =
64
60

Now, try the same number again.

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

64
60
÷ 2 =
32
30

Now, try the same number again.

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

32
30
÷ 2 =
16
15

Now, try the same number again.

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

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

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...

No good. 17 is larger than 16. So we're done reducing.

Congratulations! Here's your final answer to 3/20 + 11/12

3
20
+
11
12
=
16
15
© 2014 Randy Tayler

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