Question

The population of a city is 50,000 at present. It increases at the rate of 10% per annum. What was its population 4 years ago from present?

Answer 1

Answer:

the population of a city is 50000

increase at the rate of 10%

4 years ago rate of population is 100%

4 years after rate of population is 100%

+40%=140%

=140% of 50000=21000

4 years ago population of a city is

=50000-21000=29000

Answer 2

The population of city 4 years ago = 34,150.673 (approx)

Given:

The present population of a city is 50,000  

The rate of increase per annum = 10%  

To find:

The population of city 4 years ago

Solution:

Let x be the population of the city 4 years ago

Given that the rate increase per annum = 10%

The formula for population of city after 4 years

(i.e present population) is given by  x(1+R/100)^t  

Here, R = rate of increase

          t = time period (years)

Population after 4 years =  x(1 +10/100)⁴

= x(1+1/10)⁴

= x(1.1)⁴

=  x(1.4641)

As we know present population = 50,000

⇒ x(1.4641) = 50000

⇒ x = 50000/1.4641 = 34,150.673

Therefore,

The population of city 4 years ago = 34,150.673 (approx)

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