How do I find out the answer to this story problem?a city of 2,950,000 people has a 2.5% annual decrease in a population. What will the city's population be after 5yrs. 15yrs. and 25yrs.

Expert Answers
cburr eNotes educator| Certified Educator

Again, I disagree with raely's approach.  I think you need to calculate the 2.5% based on each year's declining population.

After one year

2,950,000 x .025 = 73,750 decrease

So, the population after one year is

2,950,000 - 73,750 = 2,876,250

After two years

2,876,250 x .025 = 71,906 decrease

2,876,250 - 71,906 = 2,804,344 population


You can do the rest of the calculation. As a check, by my calculations the population after 5 years is 2,599,232.

raely101 | Student

5 yrs- 3,318,750

10 yrs- 3,687,500

15 yrs- 4,056,250

2,950,000 times .025 times the number of years= X +2,950,000. Take the number of people and multiply by the % annual increase and then the number of years and add the original number to get theamount for that year.