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# The population of a town increases by 4% per annum and the population

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The population of a town increases by 4% per annum and the population [#permalink]
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RC_xx wrote:
gurmukh wrote:
Population after 3 years=
2000000(1.04)^3= 2249728

Posted from my mobile device

­How it is possible to solve this problem in less then 2 minutes with these, not diffucult but long calculus? Any strategies? Also all the possibile answer are very similar to each other, thus it  becomes hard to try t indentify the possible answer using approximation..

­
I got it in a bit less than 2 min. You must though be familiar with mental calculation of percentages, I used the 1% strategy and multiplied it by 4, which I thought was quicker.
My path was:

year 0: 2.000.000
year 1: 2.080.000 (20.000 is 1%, 80.000 is 4%)
year 2: 2.163.200 (20.800 is 1%, 83.200 is 4%)
year 3: 2.249.728 (21.632 is 1%, 86.528 is 4%)

Calculating 1% is simple and quick, and 4% is just 1% 4 times, and mentally multiplying by 4 is easier (by 2 by 2). Then add the result (if not familiar, manually add, it should not take long).

Hope its useful.­
The population of a town increases by 4% per annum and the population [#permalink]
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