Question

The population of town is decreased by 25% and 40% in two successive years. what percent population is decreased after two years?

Answer 1

Answer:

ans : 1.6 and 0.6

Step-by-step explanation:

Let the population be X and (X - 1)

X of 25% and 40%

=> X × 25÷ 100 = 40 ÷ 100

=> 25X ÷ 100 = 40 ÷ 100

=> X÷4 = 2 ÷ 5

=> 5X = 4×2

=> X =8÷5

=> X = 1.6

and

X - 1

=> 1.6 - 1 = 0.6

Answer 2

If there is a successive decrease in the population of the town by 25% and 40% in two successive years, then the percent population decreased after two years is 55%.

Step-by-step explanation:

The successive % decrease in 2 successive years of the population of the town is given as 25% and 40%.

We know that the formula of net percentage change for successive increase or decrease is given by

Net % change = [$a + b + \frac{ab}{100}$]%

Here a = - 25% and b = - 40% ….. [negative sign is used due to decrease in the population]  

Substituting the values in the above formula, we get

Net % change in the population after 2 years is

= [$- 25 - 40 + \frac{(-25) * (-40)}{100}$]  %

= [- 25 – 40 + (5*2)] %

= [- 25 – 40 + 10] %

= - 55% ← negative sign denotes the decrease in the population after 2 years

Thus, the population is decreased by 55% after 2 years.

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