Dear Students:This issue and several that follow it are about percents. Before you heave an exasperated sigh and intone, "Percents! When am I EVER going to use percents?" answer a few questions.

Do you ever plan to buy a house, a car, or a computer during your life?

Do you plan to pay cash for everything up front?

Or will you sometimes need a loan?

Do you hope someday to own a portfolio of stocks?

Will you ever want to open a savings account?

Do you plan to carry and use credit cards?

Would you prefer to pay sale prices for things you buy?

Or would you prefer to just go ahead and pay the full price?

As you can see, it would be hard to find a more useful mathematical skill than percents.





So now you want to learn percents.

Let's begin with a simple concept.


Consider the blue square to the right.


Let's think of this blue square as One Whole Square.








Now let's divided the square up into 100 equal pieces--every piece just the same size as every other piece.

We can easily see that every one of the 100 pieces is shaded blue.

We say that 100% of the square is shaded blue.

So, 100 % and 1 Whole are the same thing.




Take a good look at the word "percent." The "cent" part of the word goes back to the Latin word, centum, which meant 100. The "per" part for the word means "for each." So a percent tells us" how many for each hundred." 35% means 35 for each hundred, or 35 out of each hundred.








Here is our "One Whole Square" with a portion shaded green.

What percent of the square is shaded green?"








In percents, every quantity is divided into 100 pieces.

So let's divided our "One Whole Square" into 100 pieces.

Now count the pieces that are shaded green.

There are 50 pieces out of 100 shaded green.

50% of the pieces are green.






Once again our "One Whole Square" has a portion shaded, this time blue.
What percent is shaded blue?









Remember, in percents, every quantity is divided into 100 pieces.

So let's place our 100-grid over the square.

Now count the pieces that are shaded blue.

There are 86 pieces out of 100 shaded blue.

86% of the pieces are blue.






Okay, now try one for yourself.

I'll put the 100-grid over the "One Whole Square" so you can calculate the percent.

Click on the correct percent for the shaded portion of the square above.

20%

15%

13%



Calculate the percent of our "One Whole Square" that is shaded red."

Click on the correct percent for the shaded portion of the square above.

85%

75%

77%


Ready now for a little challenge?

Here is our "One Whole Square" shaded to create a design.

Click on the set of correct percents for the shaded portions of the design.

blue 37%, white 35%, tan 28 %

blue 36%, white 40%, tan 24 %

blue 40%, white 25%, tan 35 %



There! Now that was easy, wasn't it?



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"Ask Lois Terms " © 2006 Lindsay-Livingston