math help

What is 21/33 + 2/7?

What is 21/33 + 2/7?

Here's how to add

21
33
+
2
7

Step 1

Can you add yet? Nope! The denominators don't match. We need a common denominator. So next we take both denominators and multiply them. Next, take each numerator and multiply it by the denominator of the other term.

So, we multiply 21 by 7, and get 147, then we multiply 33 by 7 and get 231.

21/33 times 7

Now for the second term. You multiply 2 by 33, and get 66, then multiply 33 by 7 and get 231.

2/7 times 33

We now have a new problem, that looks like this:

147
231
+
66
231

Step 2

Since our denominators match, we can add the numerators.

147 + 66 = 213

That gives us the sum, which is

213
231

Step 3

Now, do we need to simplify this fraction?

First, we attempt to divide 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:

213
231
÷ 3 =
71
77

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...

Nope! So now we try the next greatest prime number, 29...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

Nope! So now we try the next greatest prime number, 41...

Nope! So now we try the next greatest prime number, 43...

Nope! So now we try the next greatest prime number, 47...

Nope! So now we try the next greatest prime number, 53...

Nope! So now we try the next greatest prime number, 59...

Nope! So now we try the next greatest prime number, 61...

Nope! So now we try the next greatest prime number, 67...

Nope! So now we try the next greatest prime number, 71...

Nope! So now we try the next greatest prime number, 73...

No good. 73 is larger than 71. So we're done reducing.

There you have it! Here's the final answer to 21/33 + 2/7

21
33
+
2
7
=
71
77
© 2014 Randy Tayler