math help

What is 25/15 + 8/9?

What is 25/15 + 8/9?

Let's add

25
15
+
8
9

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 9, and get 225, then we multiply 15 by 9 and get 135.

25/15 times 9

Now for the second term. You multiply 8 by 15, and get 120, then multiply 15 by 9 and get 135.

8/9 times 15

This gives us a new problem that looks like so:

225
135
+
120
135

Step 2

Since our denominators match, we can add the numerators.

225 + 120 = 345

That gives us an answer of

345
135

Step 3

Can this fraction be reduced?

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

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:

345
135
÷ 3 =
115
45

Let's try dividing by that again...

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

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

115
45
÷ 5 =
23
9

Let's try dividing by that again...

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

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

No good. 11 is larger than 9. So we're done reducing.

There you have it! Here's the final answer to 25/15 + 8/9

25
15
+
8
9
=
23
9
© 2014 Randy Tayler