CBSE 2025, Set 1

Question

If population density at a time $t+1$ is 800, Emigration = 100, Immigration = 200, Natality = 200 and Mortality = 150, calculate the population density at time $t$ and comment upon the type of age pyramid that will be formed in this case.

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** **Calculation of Population Density ($N_t$):** The formula for population density is: $$N_{t+1} = N_t + [(B + I) - (D + E)]$$ Given values: $N_{t+1} = 800$ Natality ($B$) = 200 Immigration ($I$) = 200 Mortality ($D$) = 150 Emigration ($E$) = 100 Substitute the values: $$800 = N_t + [(200 + 200) - (150 + 100)]$$ $$800 = N_t + [400 - 250]$$ $$800 = N_t + 150$$ $$N_t = 800 - 150$$ $$N_t = 650$$ **Comment on Age Pyramid:** Since the population density is increasing with time ($N_{t+1}$ is greater than $N_t$), the age pyramid formed would be of an **expanding population**.

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