Question

A number is increased by 20 % and then it is decreased by 20% . Find the net increase or decrease percent

Answer 1

Answer:

These problems are the most common with the sight of sense. If I see it by making a sense, then I will say that firstly it increases, then it decreases with the same percentage, so there's no change. But while saying so, I am wrong. how?

let's see..

Step-by-step explanation:

Let the original number be a variable (say x),

then, it increases by= 20%,

then after increasing, the amount becomes = x+(20% of x),

=x+x/5,

=6x/5.

Now it decreases by = 20%,

then new number becomes

6x/5-(20% of 6x/5),

= 6x/5- ( 6x/25),

= 24x/25,

So now, I will calculate the percentage change,

therefore by seeing the variable X and the last form 24x/25, I can definitely say that,

x>24x/25,

so there is a decrease in the number (but how much)

so, calculating the percentage change, firstly I have to calculate the main change in the number,

then x-24x/25

=X/25,

Now, I will calculate the percentage change, which is equal to:-

(X/25/X/1*100)%,

=(4)%,

or

4 percent

Therefore, there is a change of 4 percent in the whole process.

• TIPS FOR SUCH PROBLEMS

As per my experience, whenever I get such a problem, then I simply see and write the answer, without so many efforts that I have made upwards. I use a trick made by me, steps are given below:-

1. SINCE THIS TRICK IS ONLY FOR THE SITUATIONS, IN WHICH THE INCREASE PERCENTAGE AND THE DECREASE PERCENTAGES ARE SAME, you must firstly divide the percentage I by 10,
2. and then you have to square the number caught.
3. Let's take the example of the problem faced by you,

Since the percentage increase =percentage decrease, then I divide the percentage by 10, that is 20/10,

= 2,

So now I have to square the number got,

which is equal to,

(2)²= 4, which is the correct answer (see the real answer which I have solved earlier).

Answer 2

Answer:

4%

Step-by-step explanation:

let the no be x.

increase percentage = 20%

= x+20%of x

= 120x/100

decrease percentage = 20%

= 120x/100 - 20% of 120x/100

= 6x/5 - 6x/25

= 30x-6x/25

= 24x/25

total increase / decrease% = x-24x/25

= 25x-24x/25

= x/25×100

= 4%