math help

What is 3/18 + 2/7?

What is 3/18 + 2/7?

This is how you add

3
18
+
2
7

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 3 by 7, and get 21, then we multiply 18 by 7 and get 126.

3/18 times 7

Do the same for the second term. We multiply 2 by 18, and get 36, then multiply 18 by 7 and get 126.

2/7 times 18

The problem now has new fractions to add:

21
126
+
36
126

Step 2

Since our denominators match, we can add the numerators.

21 + 36 = 57

The sum we get is

57
126

Step 3

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

To find out, we try dividing 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:

57
126
÷ 3 =
19
42

Let's try dividing by that again...

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

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 19. So we're done reducing.

There you have it! Here's the final answer to 3/18 + 2/7

3
18
+
2
7
=
19
42
© 2014 Randy Tayler