math help

What is 25/15 + 5/8?

What is 25/15 + 5/8?

Here's how we add

25
15
+
5
8

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 25 by 8, and get 200, then we multiply 15 by 8 and get 120.

25/15 times 8

Now for the second term. You multiply 5 by 15, and get 75, then multiply 15 by 8 and get 120.

5/8 times 15

This gives us a new problem that looks like so:

200
120
+
75
120

Step 2

Since our denominators match, we can add the numerators.

200 + 75 = 275

So what's the answer so far?

275
120

Step 3

Can this fraction be reduced?

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

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...

Are both the numerator and the denominator evenly divisible by 5? Yes! So we reduce it:

275
120
÷ 5 =
55
24

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 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. 29 is larger than 24. So we're done reducing.

And we're done! Here's the final answer to 25/15 + 5/8

25
15
+
5
8
=
55
24
© 2014 Randy Tayler