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Friday, December 20, 2013

Benton's Percent Post


 A percent is an equivalent fraction out of 100.

 Here is how we find percents, in this example there are 40 apples.
 The 100% of the apples is 40/40
 We will be finding 50%, 25%, 10% and 1% using ratio tables.

          50%
          %   | Apples
÷2   100 | 40 /÷
     50  |   20

         25%
            %  |  Apples
÷ 4     100  |   40   /÷
    10   |    4

        10%
         %   |  Apples
÷10     100  |    40  ÷ 10
    25   |    10

     1%
         %    | Apples
÷100      100 | 40    ÷100
     1   | 0.4
Representing Percents
1) 180%

2) 12 3/4%

3) 0.7%
 
Converting Fraction-Decimal-Percent


1) 26%
26 ÷ 100 = 0.26
0.26 x 100 = 26/100

2) 7/10
7 ÷ 10 = 0.7
0.7 x 100 = 70%

3) 0.024
0.024 x 100 = 2.4%.
2.4/100

Percents


Calculator: 60 - 80% = 12                                                      Mental Math:  60 ÷ 5 = 12
                                                                                                                       100 ÷ 5 = 20

                                                                                     

               2) 0.1% of 40

 
Calculator: 40 ÷ 100 = 0.4                                                   Mental Math: 40 ÷ 1000 = 0.4
                                                                                                                  100 ÷ 1000 = 0.1
                3) 250% of 400

Calculator: 400 x 2.5 = 1000                                             Mental Math: 400 x 2 = 800 | 400 ÷ 2 = 200
                                                                                                                  800 + 200 = 1000
                                                                                                                  100 x 2 = 200 | 100 ÷ 2 = 50
                                                                                          200 + 50 = 250

Combining Percents

4.4 Pg. 149
7. A herd of 100 caribou was moved to a new location. The population increased by 10% the first year and then increased by 20% the second year.

a) Find the population after the second year.
b) Explain why there was not a 30% increase in population over the two years.

a)The population of the caribou herd after the second year was 132


The caribou herd's numbers increased by 10% the first year creating a total number of 110 caribou. The second year, the herd of caribou, now numbering 110 in total increased it's numbers by 20% for a total of 132 caribou at the end of the second year.

b) There was not a 30% increase in population over the two years because the 100% changed instead of remaining static. The 100% increased from 100 to 110 by the end of the first year and then there was a 20% increase of the current 100% raising the 100% to 132.

Discount is the money you save.
Sale Price is what you pay at the end.

4.4 Pg.148 Show You Know

 What is the final sale price at each store? Which is a better buy? Explain your thinking.

Store A: 50% off one day only
Store B: 25% off one day followed by 25% off the reduced price the second day

Example: you want to buy a $60 pair of boots.

Store A
Since 50% is equal to half, we can just half the number in question.
60 ÷ 2 = 30
The sale price is 30$
                                                  
Store B
First Day. As 25% is equal to a quarter, we can simply divide the number by 4.
60 ÷ 4 = 15                   60 - 15= 45
The sale price is now 45$
          Second Day.  We now divide the 100% (now 45$) in 4 again.

 45 ÷ 4 = 11.25                  45 - 11.25 = 33.75

The sale price is now 33.75$

Which is a better buy?

Store A is a much better choice because they're offering a $30 pair of boots compared to Store B's price of 33.75.



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