### Brandon Last Fraction Post

Sunday, May 10, 2009
Fractions. One of the scariest things to deal with in math. One of my final posts will be about dealing with numerators and denominators via adding, subtracting, dividing and multiplying.

First, adding. Example: 2/3 + 1/8.

The first step is to find a common denominator between the two. In this case, it's 24. To find the common denominator, just multiply the two denominators by each other and there you go! Then, what ever you did to the bottom, you do to the top.

2/3 + 1/8 = ?????

The common denominator is 24!

3 x 8 = 24.

2/24

8 x 2 = 16

16/24 + ? = ?????

Now, do the same to the other fraction.

1/8 = ?/24

1/8 -> x3 -> 3/24

Now, with the fractions having the same denominators, you can add them no problem!

16/24 + 3/24 = 19/24

Now, you have another problem: Subtracting. A whole new can of crap. Just do the same thing you do to add: Find the common denominator and subtract. I'll show you.

2/3 - 5/12

Incidently, the common denominator between the two is 12.

So now, the question is

8/12 - 5/12 = 3/12

= 1/4

REMEMBER: DON'T FORGET TO SIMPLIFY!!!

Fine, I'll show you how to add mixed numbers.

Take this: 10 1/2 + 6 3/4

First, let's try and turn them into improper fractions.

To do this, multiply the real number by the denominator and add whatever's on top.

So, 10 1/2 becomes 21/2 and 6 3/4 becomes 27/4.

Now, the equation is

21/2 + 27/4

Here, you can now do the same thing you would do as if it was a regular fraction.

21/2 + 27/4

21/2 x 2 = 42/4

42/4 + 27/4 = 69/4
= 17 1/4

Now, it's time to move on to another subject: multiplying.

Multiplying fractions. It's so easy a chimp could do it. Seriously. You just multiply the numerators by the numerators and the denominators by the denominators. THAT'S IT.

Let's try this example:

2/3 x 9/10

You just have to multiply the two numerators (2 x 9) and the two denominators (3 x 10)

As a result you get:

18/30

Simplified, it is 3/5.

What? Oh, you didn't get it the first time? You want me to do it again? FINE. BUT JUST ONE MORE TIME.

3/4 x 4/5

Okay, now solve it.

...

...

...

Okay, okay, I'll do the work for you...

3/4 x 4/5

3 x 4 = 12

4 x 5 = 20

Therefore, the answer must be 12/20

Now, for a subject that will really make your head hurt: Dividing fractions.

To divide fractions, you have to think in 1 of 2 ways: First, you can try and think "How many groups of (second number) go into (first number)?"

Or you can think paint can vs. room. You have used so much of a paint can to paint so much of your room. This involves taking the easy way out and making a ratio table.

First, the first method.

I'm gonna make this REAL easy.

1 1/2 / 1/2

You just have to find how many groups of 1/2 go into 1 1/2.

SOLVE.

...

...

OKAY, I'LL SOLVE IT FOR YOU, BUT THIS IS THE LAST TIME.

1 1/2 / 1/2

YOU HAVE TO FIND HOW MANY GROUPS OF 1/2 GO INTO 1 1/2

To do this, you have to make the mixed number improper.

When you do, the number becomes 3/2.

It becomes THREE HALVES.

You have to find how many groups of ONE HALVE go into THREE HALVES.

If you didn't know, the answer is 3.

Okay, let's try this with another question and method.

3/4 / 1/3.

Let's try this with a ratio table this time.

3/4 1/3*
9/4 3/3 If we multiply by 3*, we can get a whole number.

As we all know, when you divide a number by 1 you get the number.

So the answer is 9/4 or 2 1/4