math help

What is 25/15 + 6/7?

What is 25/15 + 6/7?

Here's how we add

25
15
+
6
7

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 7, and get 175, then we multiply 15 by 7 and get 105.

25/15 times 7

Now for the second term. You multiply 6 by 15, and get 90, then multiply 15 by 7 and get 105.

6/7 times 15

This gives us a new problem that looks like so:

175
105
+
90
105

Step 2

Since our denominators match, we can add the numerators.

175 + 90 = 265

So what's the answer so far?

265
105

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:

265
105
÷ 5 =
53
21

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. 23 is larger than 21. So we're done reducing.

And we're done! Here's the final answer to 25/15 + 6/7

25
15
+
6
7
=
53
21
© 2014 Randy Tayler