Problems on Population Growth
Problems on Population Growth
In our day to day life we observe that there are things or entities like population of city, the value of property, the height of a tree, weight and height of a child, the number of bacteria etc. which increase in magnitude over a period of time.
Growth: The relative increase in a quantity or entity is called growth .
Rate of Growth: Growth per unit of time is called the rate of growth.
Formulae for population Growth:
Formula 1: Let P be the population of a city or a town at the beginning of a certain year and the population grows at a constant rate of R% per annum, then
Population after n years =
Formula 2: Let P be the population of a city or a town at the beginning of a certain year. if the population grows at the rate of during second year, then
Population after 2 years =
This formula may be extended for more than 2 years.
Formula 3: Let P be the population of a city or a town at the beginning of a certain year. If the population decreases at the rate of R% per annum, then
Population after n years =
Illustration: The population of a village is 20000. If the annual birth rate is 4 % and the annual death rate 2%., calculate the population after two years.
Solution: We have,
Annual birth rate = 4%
Annual death rate = 2%
So, Annual growth = ( 4 - 2) = 2 %
Thus, we have
P = Initial population = 20000, Rate of growth = 2% per annum, n = 2 years
So, Population after 2 years =
Hence population of the town after 2 years = 20808.
1000 workers were employed to construct a river bridge in four years. At the end of first year, 10% workers were retrenched. At the end of second year, 5% of the workers at that time were retrenched . However to complete the project in time the number of workers was increased by 10% at the end of third year. How many workers were working during the fourth year? | |||
| Right Option : C | |||
| View Explanation | |||
The bacteria in a culture grows by 10% in the first hour, decreases by 10% in the second hour and increases by 10% in the third hour.If the original count of the bacteria in a sample is 10000, find the bacteria count at the end of three hours. | |||
| Right Option : B | |||
| View Explanation | |||
24000 blood donors were registered with a charitable hospital. The number of donors increased at the rate of 5% every six months. Find the time period at the end of which the total number of blood donors becomes 27783. | |||
| Right Option : A | |||
| View Explanation | |||
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