math help

What is 3/20 + 3/8?

What is 3/20 + 3/8?

This is how to add

3
20
+
3
8

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 8, and get 24, then we multiply 20 by 8 and get 160.

3/20 times 8

Do the same for the second term. We multiply 3 by 20, and get 60, then multiply 20 by 8 and get 160.

3/8 times 20

The problem now has new fractions to add:

24
160
+
60
160

Step 2

Since our denominators match, we can add the numerators.

24 + 60 = 84

This yields the answer

84
160

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:

84
160
÷ 2 =
42
80

Now, try the same number again.

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

42
80
÷ 2 =
21
40

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...

Nope. Try the next prime number, 19...

Nope. Try the next prime number, 23...

No good. 23 is larger than 21. So we're done reducing.

Congratulations! Here's your final answer to 3/20 + 3/8

3
20
+
3
8
=
21
40
© 2014 Randy Tayler