# Environmental Engineering Questions and Answers – Population Forecasting

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Population Forecasting”.

1. In which method of population forecasting, increase in population from decade to decade is assumed constant?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method

Explanation: In the arithmetic increase method, Dp/dt = K where Dp/dt = rate of change of population and K is a constant. So, the increase in the population from decade to decade is assumed constant.

2. What is the expression used for population forecasting by the arithmetical increase method?
a) PO (1 + R/100)n
b) PO + n*x
c) PO + n*x + ( n(n+1)/2 )*y
d) PO – n*x

Explanation: The expression of the arithmetical increase method is given by PO+n*x, where PO is the present population, x is the average of the population increase in known decade and n is the number of decades.

3. In which method of population forecast, percentage increase in population from decade to decade is assumed constant?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method

Explanation: In the geometrical increase method, percentage increase in population from decade to decade is assumed constant. Percentage increase in population is found from a population of 3 or 4 decades and then its average is found.

4. What is the expression used for population forecasting by the geometrical increase method?
a) PO (1 + R/100)n
b) PO + n*x
c) PO + n*x + (n (n+1) /2) *y
d) PO – n*x

Explanation: The expression of geometrical increase method is given by PO (1 + R/100) n
where PO is the present population, R is the average percentage growth rate per decade and n is the number of decades.

5. Which method of population forecast combines both arithmetical increase and geometrical increase method?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method

Explanation: In the incremental increase method, the population for the next decade is found by adding to the present population, the average increase plus the average incremental increase per decade, hence combines both arithmetical and geometrical methods.
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6. What is the expression used for population forecasting by the incremental increase method?
a) PO (1 + R/100)n
b) PO + n*x
c) PO + n*x + (n (n+1) /2) *y
d) PO – n*x

Explanation: The expression of the incremental increase method is given by PO + n*x + (n (n+1) /2) *y where PO is the present population, x is the average of the population increase in known decade, y is the average of incremental increase and n is the number of decades.

7. Logistic method is also called as _______
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method

Explanation: Logistic method is also called a decreased rate of growth method. In this method, the percentage increase in growth rate and then the percentage decrease in growth rate are founded where all populations grow according to the logistic curve.

8. Consider the following statements.
i. The arithmetical increase method is suitable for new cities
ii. The decreasing growth rate method is used where the rate of growth shows a downward pattern
iii. The geometrical increase method is used for older cities
Which of the following above statements is/are correct?
a) i, ii, iii
b) i and iii
c) Only ii
d) ii and iii

Explanation: Arithmetical increase method is suitable for older cities, whereas a geometrical increase method is suitable for new cities.

9. Which method is suitable if the growth rate is decreasing and the population is reaching towards saturation?
a) Arithmetical increase method
b) Graphical comparison method
c) Zoning method
d) Decreased rate of growth method

Explanation: In decreased rate of growth method, growth rate is decreasing and the population is reaching towards saturation and is only valid when growth rate shows a downward pattern.

10. Which method of population forecast is suitable when extension is required for small duration and past record is available for long duration?
a) Graphical comparison method
b) Graphical extension method
c) Logistic curve method
d) Zoning method

Explanation: In the graphical extension method, a curve is drawn between population and time up to the present period, then the curve is extended from present to the future decade and the population is approximately determined from the extended part of the curve.

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