SHORT TRICKS APPLIED IN PERCENTAGE

1. If the value of something is increased by x % and again increased by y % then resulting effect in percent

Total change = {x+y+x*y/100}

Example :

The Salary of a worker is first increased by 10% and thereafter increased by 5%. What is the overall change in percent.

Solution:

overall change = + 10 + 5 + (+10)(+5)/100 = +15.5 % (increased)

use (+) sign for increment and (-) sign for decrement.

2.If the value of something is increased by x % then decreased by y % then resulting effect in percent

Total change = {+x- y+ (x*(-y)/100)}

Example :

The Salary of a worker is first increased by 10% and thereafter decreased by 5%. What is the overall change in percent.

Solution:

overall change = + 10 – 5 +(10)(-5)/100 = +4.5 % (increased)

use (+) sign for increment and (-) sign for decrement.

3.If the value of something is decreased by x % and again decreased by y % then resulting effect in percent

Total change = {-x – y + (-x)*(-y)/100}

Example :

The Salary of a worker is first decreased by 10% and thereafter decreased by 5%. What is the overall change in percent.

Solution:

overall change = – 10 – 5+ (-10)(-5)/100 = -14.5 % (decreased)

use (+) sign for increment and (-) sign for decrement.

Now, this is just the formula but its application are endless in the question of percentage , for the questions like

1. If both the lengths (%) and breadth(%) of a rectangle are changed find the change in area(%) ?

2. If the speed and time of a vehicle are changed, find the change in distance ?

Similarly in all those questions where two quantities are multiplied to produce third one

rate * time = cost

efficiency * time = work

average * no. of elements = total value

rate * quantity = price (expenditure)