·Percentage is a method of representing any quantity in fraction of 100 i.e. out of 100 how much is that quantity.
·It is often denoted using the percent sign, "%"
·One percent (1%) means 1 per 100 and 100% means all and so on..
Points to Remember:
·1/5th of a number = 1/5 ×100 = 20%
·20% of a mumber = 20/100 = 1/5th of that number.
·If a number is increased from value A to B then % increase = (B-A)/A × 100
·If a number is decreased from value A to B then % decrease = (A-B)/A ×100
·If x% and y% are two successive increase(+ve) or decrease(-ve) in a number then overall percentage of change = x + y + xy/100
·If the population of a city increases (+ve) or decreases(-ve) by r% every year then,
I. Population after n year = Present Population ×(1+ r/100)n
II. Population n years ago = Present Population ×(100/(100+r))n
·What is the percent value A to B = A/B × 100
Now let’s understand each of above listed point with examples one by one.
Example:
Calculate 25% of 80
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25% =
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25
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100
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And
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25
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× 80 = 20
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100
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So 25% of 80 is 20
Example:
A fruit seller had some apples. He sells 40% apples and still has 420 apples. Originally, he had:
Explanation:
Suppose originally he had x apples.
Then, (100 - 40)% of x = 420.
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60 | x x = 420 |
| 100 |
| x = |
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420 x 100 |  = 700. |
| 60 |
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Example:
If the population of a city increases 20% every year and if its present population is 576000. What was the population of city 2 years ago.
Explanation:
This is an example of two successive change.
Population n years ago =Present Population ×(100/(100+r))n
= 576000×(100/(100+20))n
= 400000
Example:
What percentage of 5 is 3
Explanation:
=3/5×100
= 60%