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Lesson 28  Section 2

Percent increase or decrease

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Example 1.   A blouse that usually sells for $32 is on sale at 25% off.  How much do you pay?

Answer.  "25% off" means that a quarter of the price will be subtracted. A quarter of 32 is 8.  (Lesson 15.)  Therefore you will pay $8 less.  You will pay $32 − $8 = $24.

Example 2.   A VCR that usually sells for $180 is being sold at a

  discount of 33 1
3
%.  How much do you pay?
  Answer.  A "discount of 33 1
3
%" means that a third of the price will be

taken off.  A third of 180 is 60. (Lesson 16, Question 1.)  You will pay

$180 − $60 = $120.

Example 3.   A CD that last week sold for $15 now costs 10% more.  How much does it cost now?

Answer.  10% of $15 is $1.50. (Lesson 4, Question 8.)  Therefore it now costs

$15 + $1.50 = $16.50.

Example 4.  Calculator problem.   An item costs $39.95, and the tax

  is 8 3
4
%.  How much will you pay for the item?

Solution.   On simple calculators, press

3 9 . 9 5 × 8 . 7 5 % +

That is, press the + key.  Do not press = .  See

 43.445625 

You will pay $43.45.

Alternatively, the total cost is 100% of the item plus 8.75%, which is a total of 108.75%.  Press

3 9 . 9 5 × 1 0 8 . 7 5 %

Example 5.   Calculator problem   Marlene's rent was $672.50.  It was reduced by 6½%. What is her present rent?

 Solution.   This time press − .  Press

6 7 2 . 5 × 6 . 5 %

See

 628.7875 

Her present rent is $628.79.

Estimations

When using a calculator, and in general, the student should have some idea as to where the answer lies.  With a calculator it is very easy to press a wrong button.

Example 6.   How much is 26.2% of $44.59?  Choose the best answer:

$.11    $1.10     $11    $110

Answer.  $11.  Because 26.2% is close to 25%, which is a quarter.  A quarter of 44 is 11.

Example 7.   How much is 49. 3% of $205.16?  Choose the best answer:

$1,020   $102    $10.20    $1.02

Answer.  $102.   49. 3% is close to 50%, which is half.

Example 8.   98 is approximately what percent of 204?

16%    48%    52%    89%

Answer.   48%.  Because 98 is a little less than half of 204.

Example 9.    What percent of 40 is 11?

6%   24%   27%    9%

Answer.   27%.  Because 11 is a little more than a quarter (25%) of 40, which is 10.


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