math help

What is 25/15 + 2/8?

What is 25/15 + 2/8?

Let's add

25
15
+
2
8

Step 1

Of course, you can't add two fractions if the denominators (bottom numbers) don't match. To get a common denominator, multiply the denominators together. Then we fix the numerators by multiplying each one by their other term's denominator.

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

25/15 times 8

Do the same for the second term. We multiply 2 by 15, and get 30, then multiply 15 by 8 and get 120.

2/8 times 15

The problem now has new fractions to add:

200
120
+
30
120

Step 2

Since our denominators match, we can add the numerators.

200 + 30 = 230

This yields the answer

230
120

Step 3

The last step is to reduce the fraction if we can.

To find out, we try dividing it by 2...

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

230
120
÷ 2 =
115
60

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...

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

115
60
÷ 5 =
23
12

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. 13 is larger than 12. So we're done reducing.

And we're done! Here's the final answer to 25/15 + 2/8

25
15
+
2
8
=
23
12
© 2014 Randy Tayler