Directions: Answer the questions based on the information given below...
The population of town A in the third year = 180600
It increased by 3% and 7.5% in the second and third year respectively.
The population of town A in the second year = 180600/1.075 = 168000
The population of town A in the first year = 168000/1.05 = 160000
The population of town B in the second year was equal to 150% of the population of town A in the first year.
The population of town B in the second year = 160000×1.50 = 240000
The population of town B increased by 25% in the second year.
Therefore, the population of town B in the first year = 240000/1.25 = 192000
The population growth rate of town B in the third year was half of that of the previous year means 25/2 = 12.5%
So, the population of town B in the third year = 240000×1.125 = 270000
The area of town C is 1250 km2 and the population density for the second year was 250.
Therefore, the population of town C in the second year = 250×1250 = 312500
The growth rate for town C was 11.11% and 10% for the second and the third year respectively.
So, the population of town C in the first year = 312500/1.111 = 281250
The population of town C in the third year = 312500×1.10 = 343750
Let the total population of town D in the third year = x
The difference between the total population of town D in the third year and the total population of town A in the first year = The difference between the total population of town B in the second year and the total population of town D in the third year.
So, x - 160000 = 240000 - x
x = 200000
Area of city D = 20%×1250 = 250 km2
Population density of town D = 200000/250 = 800 per km2
Required difference = 270000 - 168000 = 102000
Hence, the correct answer is 102000.