Following is a question from Manhattan GMAT CAT.
Boomtown urban planners expect the city’s population to increase by 10% per year over the next two years. If that projection were to come true, the population two years from now would be exactly double the population of one year ago. Which of the following is closest to the percent population increase in Boomtown over the last year?
A. 20%
B. 40%
C. 50%
D. 65%
E. 75%
The answer explanation considers 10% increase as successive increase - If population is X today, it will be 1.1*X next year and 1.1*1.1*X following year. I was not sure and I had done both above and 1.20*X.
Since this specific question asks for an approximate answer, it was okay but I have a generic question - how do we know in such questions whether to use successive % or use same % for the entire period?
Boomtown urban planners expect the city’s population to increase by 10% per year over the next two years. If that projection were to come true, the population two years from now would be exactly double the population of one year ago. Which of the following is closest to the percent population increase in Boomtown over the last year?
A. 20%
B. 40%
C. 50%
D. 65%
E. 75%
The answer explanation considers 10% increase as successive increase - If population is X today, it will be 1.1*X next year and 1.1*1.1*X following year. I was not sure and I had done both above and 1.20*X.
Since this specific question asks for an approximate answer, it was okay but I have a generic question - how do we know in such questions whether to use successive % or use same % for the entire period?
