math help

What is 7/21 + 1/3?

What is 7/21 + 1/3?

Here's how we add

7
21
+
1
3

Step 1

We have to make sure the denominators are equal.

Since 3 is evenly divided by 21, we can multiply just one term to get a common denominator.

Multiply 1 by 7, and get 7, then we multiply 3 by 7 and get 21.

1/3 times 7

So now our fractions look like this:

7
21
+
7
21

Step 2

Since our denominators match, we can add the numerators.

7 + 7 = 14

So the answer is:

14
21

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...

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...

No good. So next you try the next prime number, which is 7...

Are both the numerator and the denominator evenly divisible by 7? Yes! So we reduce it:

14
21
÷ 7 =
2
3

So far so good... let's try to divide by that number again.

No good. 7 is larger than 2. So we're done reducing.

And we're done! Here's the final answer to 7/21 + 1/3

7
21
+
1
3
=
2
3
© 2014 Randy Tayler