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 = x Original Salary = 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.

New Salary = x Original Salary = x 500 = 475

In general,

If an amount “” as increased by

If an amount “” as decreased by