math help

What is 5/100 + 3/8?

What is 5/100 + 3/8?

Here's how we add

5
100
+
3
8

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 5 by 8, and get 40, then we multiply 100 by 8 and get 800.

5/100 times 8

Do the same for the second term. We multiply 3 by 100, and get 300, then multiply 100 by 8 and get 800.

3/8 times 100

So now our fractions look like this:

40
800
+
300
800

Step 2

Since our denominators match, we can add the numerators.

40 + 300 = 340

Now we have an answer.

340
800

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...

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

340
800
÷ 2 =
170
400

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:

170
400
÷ 2 =
85
200

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...

No good. So next you try the next prime number, which is 5...

Are both the numerator and the denominator evenly divisible by 5? Yes! So we reduce it:

85
200
÷ 5 =
17
40

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 7...

No good. So next you try the next prime number, which is 11...

No good. So next you try the next prime number, which is 13...

No good. So next you try the next prime number, which is 17...

No good. So next you try the next prime number, which is 19...

No good. 19 is larger than 17. So we're done reducing.

And we're done! Here's the final answer to 5/100 + 3/8

5
100
+
3
8
=
17
40
© 2014 Randy Tayler