math help

What is 4/10 + 1/8?

What is 4/10 + 1/8?

This is how you add

4
10
+
1
8

Step 1

Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term.

So, we multiply 4 by 8, and get 32, then we multiply 10 by 8 and get 80.

4/10 times 8

Now for the second term. You multiply 1 by 10, and get 10, then multiply 10 by 8 and get 80.

1/8 times 10

We now have a new problem, that looks like this:

32
80
+
10
80

Step 2

Since our denominators match, we can add the numerators.

32 + 10 = 42

That gives us the sum, which is

42
80

Step 3

Now, do we need to simplify this fraction?

First, we attempt to divide it by 2...

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

42
80
÷ 2 =
21
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 3...

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

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. So next you try the next prime number, which is 23...

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

And we're done! Here's the final answer to 4/10 + 1/8

4
10
+
1
8
=
21
40
© 2014 Randy Tayler