math help

What is 4/40 + 8/9?

What is 4/40 + 8/9?

Here's how you add

4
40
+
8
9

Step 1

We still have different denominators (bottom numbers), though, so we need to get a common denominator. This will make the bottom numbers match. Multiply the denominators together first. Now, multiply each numerator by the other term's denominator.

Now we multiply 4 by 9, and get 36, then we multiply 40 by 9 and get 360.

4/40 times 9

Now for the second term. You multiply 8 by 40, and get 320, then multiply 40 by 9 and get 360.

8/9 times 40

This gives us a new problem that looks like so:

36
360
+
320
360

Step 2

Since our denominators match, we can add the numerators.

36 + 320 = 356

So what's the answer so far?

356
360

Step 3

Can this fraction be reduced?

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

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

356
360
÷ 2 =
178
180

Now, try the same number again.

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

178
180
÷ 2 =
89
90

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...

Nope. Try the next prime number, 29...

Nope. Try the next prime number, 31...

Nope. Try the next prime number, 37...

Nope. Try the next prime number, 41...

Nope. Try the next prime number, 43...

Nope. Try the next prime number, 47...

Nope. Try the next prime number, 53...

Nope. Try the next prime number, 59...

Nope. Try the next prime number, 61...

Nope. Try the next prime number, 67...

Nope. Try the next prime number, 71...

Nope. Try the next prime number, 73...

Nope. Try the next prime number, 79...

Nope. Try the next prime number, 83...

Nope. Try the next prime number, 89...

Nope. Try the next prime number, 97...

No good. 97 is larger than 89. So we're done reducing.

Congratulations! Here's your final answer to 4/40 + 8/9

4
40
+
8
9
=
89
90
© 2014 Randy Tayler