S k i l l
 i n
A R I T H M E T I C

Table of Contents | Home | Introduction

PERCENTS ARE RATIOS

Lesson 27  Section 2

Percent increase or decrease

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 14.)  Therefore you will pay $8 less.  You will pay $32$8 = $24.

Example 2.   A VCR that usually sells for $240 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 240 is 80.  (Lesson 15, Question 2.)  You will pay

$240minus$80 = $160.

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.  (To take 10% -- a tenth -- separate one decimal place.  Section 1, Example 7.)  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 where the answer lies.  With a calculator it is very easy to press a wrong number.

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 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.


Please "turn" the page and do some Problems.

or


Introduction | Home | Table of Contents

Please make a donation to keep TheMathPage online.
Even $1 will help.

Copyright © 2001-2007 Lawrence Spector

Questions or comments?

E-mail:  themathpage@nyc.rr.com