math help

What is 20/64 + 4/5?

What is 20/64 + 4/5?

This is how you add

20
64
+
4
5

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 20 by 5, and get 100, then we multiply 64 by 5 and get 320.

20/64 times 5

Now for the second term. You multiply 4 by 64, and get 256, then multiply 64 by 5 and get 320.

4/5 times 64

This gives us a new problem that looks like so:

100
320
+
256
320

Step 2

Since our denominators match, we can add the numerators.

100 + 256 = 356

So what's the answer so far?

356
320

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
320
÷ 2 =
178
160

Let's try dividing by that again...

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

178
160
÷ 2 =
89
80

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 3...

Nope! So now we try the next greatest prime number, 5...

Nope! So now we try the next greatest prime number, 7...

Nope! So now we try the next greatest prime number, 11...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

Nope! So now we try the next greatest prime number, 29...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

Nope! So now we try the next greatest prime number, 41...

Nope! So now we try the next greatest prime number, 43...

Nope! So now we try the next greatest prime number, 47...

Nope! So now we try the next greatest prime number, 53...

Nope! So now we try the next greatest prime number, 59...

Nope! So now we try the next greatest prime number, 61...

Nope! So now we try the next greatest prime number, 67...

Nope! So now we try the next greatest prime number, 71...

Nope! So now we try the next greatest prime number, 73...

Nope! So now we try the next greatest prime number, 79...

Nope! So now we try the next greatest prime number, 83...

No good. 83 is larger than 80. So we're done reducing.

There you have it! Here's the final answer to 20/64 + 4/5

20
64
+
4
5
=
89
80
© 2014 Randy Tayler