POPULATION GROWTH WITH DIFFERENT PERCENTAGE & DIFFERENT TIME DURATION -
Let there be an increase in population at R₁% during 1st year and R₂% during 2nd year
R₁ R₂
Then population after 2 years = P X ( 1 + ------ ) X ( 1 + ------ )
100 100
Example.1) Present population of a town is 1200000, if the population increase by 10% on 1st year, 15% in 2nd year, and in 3rd year increased by 10%, then calculate what will be the population after 3rd year.
Ans.) As we know from the above statement, 1st year increased by R₁ = 10%, 2nd year increased by R₂ = 15%, and 3rd year increased by R₃ = 10%. As we know the formulae –
Then population after 3 years =
R₁ R₂ R₃
P X ( 1 + ------- ) X ( 1 + ------- ) X ( 1 + ------- )
100 100 100
10 15 10
= 1200000 X ( 1 + ------ ) X ( 1 + ------ ) X ( 1 + ------ )
100 100 100
11 23 11
= 1200000 X ------- X -------- X --------
10 20 10
= 600 X 11 X 23 X 11 = 1669800
So, the population after 3 years would be 1669800 (Ans.)