# Percentage Changing

The change in the value of an item can be expressed as a percentage increase or decrease of the original value.
An increase of 5% in the salary of a men who earns Rs.500 per month. That means, there is an increase of Rs.5 For every hundred (100). i.e. after increase, Rs.100 becomes 105.
Therefore,

New Salary = $\frac{{105}}{{100}}$ x Original Salary = $\frac{{105}}{{100}}$ x 500 = 525
On the other hand, a decrease of 5% in his salary means that for every Rs.100 in the original salary, there is a decrease of Rs.5 i.e. each Rs.100 becomes Rs.95
i.e.

$\therefore \frac{{{\text{New Salary}}}}{{{\text{Original Salary}}}} = \frac{{95}}{{100}}$
New Salary = $\frac{{95}}{{100}}$ x Original Salary = $\frac{{95}}{{100}}$ x 500 = 475
In general,
If an amount “$a$” as increased by $b\%$
$\therefore \boxed{{\text{New Amount = }}\frac{{{\text{(a + 100)}}}}{{{\text{100}}}}{\text{ x (}}a{\text{)}}}$
If an amount “$a$” as decreased by $b\%$

$\therefore \boxed{{\text{New Amount = }}\frac{{{\text{(a - 100)}}}}{{{\text{100}}}}{\text{ x (}}a{\text{)}}}$