Percent

Discussion

Percent is a ratio of some number to 100.
It is usually found by:
- finding the maximum possible value for something
- finding the value that was achieved
- dividing the two.
- This will yield a number between 0 and 1, so multiply it by 100
Example 1: Bob was tossing darts at the a dartboard. The threw 15 darts and hit the board 12 times. What is his hit percentage?
```
    Maximum value:  15
    Value Achieved: 12

    Ratio  12/15 = .8 
    Percentage:   .8 × 100 = 80%
    
```

If we want to work with a percentage, we need to convert this back to a decimal number by dividing by 100.

Example 2: Sue claims be able to hit the dart board 75% of the time. If she tosses 15 darts, how many darts would she expect to hit the board with?

 
  75% = .75  (or 75 hits/100 trys)

  15 trys * .75 = 11.25
  or we would expect sue to hit the board 11 times given 15 trys.

Percent change is a measure of how something has changed (such a prices)

Formula:

                       
                       end amount - start amount 
     percent change =  -------------------------- x 100
                              end amount

Positive indicates growth, negative indicates decline.

Example 3

 Gas prices were $3.00 per gallon, a few weeks ago.  Now the price is $2.75.  What is the percent change?

       2.75 - 3.0       -.25
       ---------   =   ------  =  - 0.0909 = -9.1% 
          2.75          2.75 

    Or a 9.1% decrease.

Example 4:

  In 2000 Pennsylvania had a population of 12,281,054	
  In 2004 Pennsylvania had a population of 12,406,292	
  What is the percent change?

  12,406,292-12,281,054       125,238
  --------------------- =   -----------  = 0.00100 = 1%
        12,406,292          12,406,292

We often deal with a price markup.

This is how stores make money.

The formula for percent markup on cost is

                       selling price  - dealer's cost 
percent markup cost = ------------------------------- × 100
                               dealer's cost

Example 5:

  If a vacuum cleaner costs a dealer $320 and sells for $699, what is the markup?

    699 - 320     379
    --------   = ----  =   1.184 = 118%
      320         320

Example 6:

If the above dealership sells these vacuums at 25% off.
    A. What is the selling price?
    B. What is the percent markup?

    discount = $699 × .25 = $174.75  
    price = $699 - $174.75 = $524.25

    markup =  524.25- 320      204.25
             ------------- =   ------  = .638 
	          320           320

    which is 64%

Homework

Please do 7 - 47 pages 599 - 601