Question
The population of a town was 1,60,000 two years ago. If it has increased by 3% and 5% respectively in the last two years, find its present population
- 163040
- 170000
- 173040
- 180000
Hint:
We are given the population of town two years back. It has increased 3% in first year and 5% in second year. We have to find the current population. We will first find total population before one year. Using this information, we will find the current population.
The correct answer is: 173040
Let the population two years back be denoted by P.
P = 160000
The increase in percentage in 1 year = 3%
The increase in percentage in 2 year = 5%
We will find the increased population after 1 year. The increased population will be sum of original population and increase in number of population. The increase in population is 3%. It is 3% of original population.
First year = P + 30% of P
= P + 
× 160000
= 160000 + 4800
= 164800
We will find the increased population after 2 years. The increased population will be sum of first year population and percentage increased in that population.
Second year population = First year + 5% First year
= 164800 + 
× 164800
= 164800 + 8420
= 173040
The current population is 173040
For such questions, we should be careful while finding the percentage increase in the population. We have to add the increased in number of population to the original population to get new population. We have to careful about order of increase in population.
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