math help

What is 21/63 + 4/11?

What is 21/63 + 4/11?

Let's add

21
63
+
4
11

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 11, and get 231, then we multiply 63 by 11 and get 693.

21/63 times 11

Now for the second term. You multiply 4 by 63, and get 252, then multiply 63 by 11 and get 693.

4/11 times 63

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

231
693
+
252
693

Step 2

Since our denominators match, we can add the numerators.

231 + 252 = 483

Answer:

483
693

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:

483
693
÷ 3 =
161
231

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...

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

161
231
÷ 7 =
23
33

Let's try dividing by that again...

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...

No good. 29 is larger than 23. So we're done reducing.

There you have it! Here's the final answer to 21/63 + 4/11

21
63
+
4
11
=
23
33
© 2014 Randy Tayler