Question

a number is first increased by 25% and then decreased by 25% find the increase or decrease percentage​

Answer 1

Let the number be 100

so, Inc. by 25 % = 125

dec. by 25 % = 125*75/100 = 93.75

Hence, it is decreased overall.

Hence, Net dec. % = 100-93.75*100/100 = 6.25 %  

Answer 2

let say number = x

number first increased by 25%

number after 25% increase = number + 25%of number

= x + (25/100)x

= x + x/4

= 5x/4

now number is decreased by 25 %

final number = 5x/4 - (25/100)(5x/4)

=(5x/4)(1 - 1/4)

= (5x/4)(3/4)

= 15x/16

original number was x

decrease in number = original number - final number

= x - 15x/16

= x/16

% decrease = {(x/16)/(x)}×100

= 100/16

= 25/4

= 6.25

number decrease by 6.25%