Question

When will the population density increase, under special conditions?
When the number of :

• A. Deaths exceeds number of births and also number of emigrants equals number of immigrants.
• B. Births plus number of immigrants equals number of deaths plus number of emigrants.
• C. Births plus number of emigrants is more than the number of deaths plus number of immigrants.
• D. Births plus number of immigrants is more than the sum of number of deaths and number of emigrants.

Answer 1

The Correct Option is D

Let:
$N_t$ = Population density at time t
B = Number of births 
D = Number of deaths
I = Number of immigrants 
E = Number of emigrants
The population density at time t+1 ($N_{t+1}$) can be calculated as:
\[ N_{t+1} = N_t + (B + I) - (D + E) \]
Population density will increase when $N_{t+1} > N_t$. This means:
N_t + (B + I) - (D + E) &> N_t 
(B + I) - (D + E) &> 0
(B + I) &> (D + E)
Therefore, population density increases when the number of births plus the number of immigrants (B + I) is greater than the number of deaths plus the number of emigrants (D + E).