Question

Present population of a community is 28000 with an average water consumption of $4200m^3/d$. The existing water treatment plant has a design capacity of $6000m^3/d$. It is expected that the population will increase at 44000 during the next 20 years. The number of years from now when the plant will reach its design capacity, assuming an arithmetic rate of population growth, will be

• A. 5.5 years
• B. 8.6 years
• C. 16.5 years
• D. 15.0 years

Answer 1

The correct option is D 15.0 years

$4200m^3/d\text{water consumption is by population of}28000$.
$6000m^3/d\text{water consumption will be by population of}\frac{28000}{4200}\times 6000=40000person$

$Presentpopulation=28000$

After 20 years, Population = 44000

Increase in population per year
$=\frac{44000-28000}{20}=800$

Number of years required to reach population equal to 40000
$=\frac{40000-28000}{800}=15years$