## me123456789 2 years ago the beginning of 1975 the population of a country was 40 million and growing at a rate of 3% per year. Assume that the growth is exponential. Estimate the population of the country at the beginning of the year 2010

1. Rohangrr

of course 80 million

2. me123456789

im sorry and how did you get this?

3. me123456789

plz help

4. mubzz

This can be taken as a geometric progression where the population at any given year is given by $ar ^{n-1}$ where a is starting population and 'r' in this case is 1.03 as the population is increasing. Now count the years, from 1975 to 2010, 35 years. So you use formula population = $40000000\times1.03^{35}$ population approx 112 million

5. me123456789

i got 83751117 how did you get 112 mil?

6. mubzz

how did you get that? Because I've used exponential population growth method and geometric progression and got the same answer

7. me123456789

ok i rechecked it ant got 1.05 and the answer was 135mil

8. mubzz

ok let me g through it again. two mins :)

9. me123456789

40000000*1.05^24 was 129003997.7

10. mubzz

it can't be 1.05 as you gave the growth rate to be 3% If it is 5%, then you get 40(1.05)^35 = 220 million Check your question again. You get 135 million if the growth rate is 5% and the time period is 1975 to 2000

11. me123456789

yeah the years are 1975 to 2010

12. me123456789

nm

13. me123456789

can you help me with this one?

14. me123456789

If the population of bacteria doubles in 4 hours how long will it take for it to triple its original size