The population of a city increase each year by 4%.

The population of a city increase each year by 4% of what it had been at the beginning of each year. If its present population is 6760000, find:
(i) its population 2 years hence
(ii) its population 2 years ago.

Solution:

It is given that
Present population = 6760000
Increase percent = 4% p.a.
(i) We know that
Population 2 years hence = P (1 + r/100)²
Substituting the values
= 6760000 (1 + 4/100)²
By further calculation
= 6760000 × 26/25 × 26/25
= 7311616
(ii) We know that A = 6760000
Population 2 years ago P = A + (1 + r/100)²
Substituting the values
= 6760000 + (1 + 4/100)²
By further calculation
= 6760000 + (26/25)²
= 6760000 × 25/26 × 25/26
= 6250000

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