Question

Exercise 7.3
A number is increased by 40%, then decreased by 40%. Find the net increase or decrease percentage.​

Answer 1

Answer:

16%

Step-by-step explanation:

Let us assume that the number be 100. At first we have to increase the number by 40%. Then we have to decrease 40% again.

so, firstly, after increase the term by 40% , we have the number be

100 + 100*40/100

= 100 + 40

= 140

Again, we have to decrease the number by 40%. So, the number becomes

140 - 140*40/100

= 140 - 56

= 84

So, we have seen that the number decrease. Now we have to calculate the percentage of the number has decreased.

Assumed number = 100

Present number = 84

So, decrease percentage = 16 % (ans.)16%

Answer 2

16%

Step-by-step explanation:

let no.be = X

after increase

new no.=X+X×40/100

=100X+40x/100

=140x/100

= 7x/5

after decrease

new no.= 7x/5-7x/5×40/100

=7x/5(1-4/10)

= 7x / 5(10-4)/10

= 7x/5×6/10

= 21/25x

decrease = x -21/25

x=4/25

%decrease= 4/25x/ x ×100

= 4/25×100

= 16%