math help

What is 25/15 + 1/7?

What is 25/15 + 1/7?

This is how to add

25
15
+
1
7

Step 1

We can't add two fractions with different denominators (the bottom number). So you need to get a common denominator - both bottom numbers need to match. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 25 by 7, and get 175, then we multiply 15 by 7 and get 105.

25/15 times 7

Do the same for the second term. We multiply 1 by 15, and get 15, then multiply 15 by 7 and get 105.

1/7 times 15

So now our fractions look like this:

175
105
+
15
105

Step 2

Since our denominators match, we can add the numerators.

175 + 15 = 190

So the answer is:

190
105

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

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

Nope! So now we try the next greatest prime number, 3...

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:

190
105
÷ 5 =
38
21

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...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

No good. 23 is larger than 21. So we're done reducing.

There you have it! Here's the final answer to 25/15 + 1/7

25
15
+
1
7
=
38
21
© 2014 Randy Tayler