math help

What is 20/64 + 9/12?

What is 20/64 + 9/12?

Here's how to add

20
64
+
9
12

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 12, and get 240, then we multiply 64 by 12 and get 768.

20/64 times 12

Now for the second term. You multiply 9 by 64, and get 576, then multiply 64 by 12 and get 768.

9/12 times 64

This gives us a new problem that looks like so:

240
768
+
576
768

Step 2

Since our denominators match, we can add the numerators.

240 + 576 = 816

That gives us an answer of

816
768

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:

816
768
÷ 2 =
408
384

Let's try dividing by that again...

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

408
384
÷ 2 =
204
192

Let's try dividing by that again...

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

204
192
÷ 2 =
102
96

Let's try dividing by that again...

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

102
96
÷ 2 =
51
48

Let's try dividing by that again...

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

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

51
48
÷ 3 =
17
16

Let's try dividing by that again...

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...

No good. 17 is larger than 16. So we're done reducing.

There you have it! Here's the final answer to 20/64 + 9/12

20
64
+
9
12
=
17
16
© 2014 Randy Tayler