Question

Please solve my doubt:

1)A number is increased by 25% and then reduced by 25%.Find the net increase or decrease percent.

2) A number is increased by 10% and then decreased by 10%.Find the net increase or decrease percent.

Note : My doubt is that please kindly,I request you that solve both the questions with a exactly same process/formula.
​

Answer 1

1) No increase or decrease

2) No increase or decrease

Answer 2

6.25% , 1%

Step-by-step explanation:

(1) formula: a + b + (ab/100)

use +ve sign for increase & -ve sign for decrease

a = 25 , b = -25

So 25 - 25 + ((25(-25)/100 = -6.25 (-ve means decrease)

net decrease = 6.25 %

similarly

(2) 10 - 10 + 10×(-10)/100 = -1

decrease = 1%

second method:(1) if both increase & decrease value is same then finally there will be decrease

= x^2/100 = 25^2/100

= 6.25%

similarly, (2) decrease % = 10^2/100 = 1%

third method (Ratio method):

Q(1) 25% =25/100 = 1/4

I : F

4 : 5

4 : 3

_____

16 : 15

_____. net decrease = 16-15 = 1 units

decrease% = 1/16 × 100 = 6.25%

Q(2)

10% = 1/10

I : F

10 : 11

10 : 9

_______

100 : 99

_______, decrease = 100- 99 = 1 units

decrease % = 1/100 * 100 = 1%