math help

What is 15/60 + 6/7?

What is 15/60 + 6/7?

Here's how we add

15
60
+
6
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 15 by 7, and get 105, then we multiply 60 by 7 and get 420.

15/60 times 7

Do the same for the second term. We multiply 6 by 60, and get 360, then multiply 60 by 7 and get 420.

6/7 times 60

So now our fractions look like this:

105
420
+
360
420

Step 2

Since our denominators match, we can add the numerators.

105 + 360 = 465

So the answer is:

465
420

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. Try the next prime number, 3...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

465
420
÷ 3 =
155
140

Now, try the same number again.

Nope. Try the next prime number, 5...

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

155
140
÷ 5 =
31
28

Now, try the same number again.

Nope. Try the next prime number, 7...

Nope. Try the next prime number, 11...

Nope. Try the next prime number, 13...

Nope. Try the next prime number, 17...

Nope. Try the next prime number, 19...

Nope. Try the next prime number, 23...

Nope. Try the next prime number, 29...

No good. 29 is larger than 28. So we're done reducing.

Congratulations! Here's your final answer to 15/60 + 6/7

15
60
+
6
7
=
31
28
© 2014 Randy Tayler