math help

What is 20/64 + 7/10?

What is 20/64 + 7/10?

This is how we add

20
64
+
7
10

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 10, and get 200, then we multiply 64 by 10 and get 640.

20/64 times 10

Now for the second term. You multiply 7 by 64, and get 448, then multiply 64 by 10 and get 640.

7/10 times 64

This gives us a new problem that looks like so:

200
640
+
448
640

Step 2

Since our denominators match, we can add the numerators.

200 + 448 = 648

So what's the answer so far?

648
640

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:

648
640
÷ 2 =
324
320

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:

324
320
÷ 2 =
162
160

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:

162
160
÷ 2 =
81
80

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. So next you try the next prime number, which is 29...

No good. So next you try the next prime number, which is 31...

No good. So next you try the next prime number, which is 37...

No good. So next you try the next prime number, which is 41...

No good. So next you try the next prime number, which is 43...

No good. So next you try the next prime number, which is 47...

No good. So next you try the next prime number, which is 53...

No good. So next you try the next prime number, which is 59...

No good. So next you try the next prime number, which is 61...

No good. So next you try the next prime number, which is 67...

No good. So next you try the next prime number, which is 71...

No good. So next you try the next prime number, which is 73...

No good. So next you try the next prime number, which is 79...

No good. So next you try the next prime number, which is 83...

No good. 83 is larger than 81. So we're done reducing.

And we're done! Here's the final answer to 20/64 + 7/10

20
64
+
7
10
=
81
80
© 2014 Randy Tayler