VeritasPrepKarishma wrote:

ssriva2 wrote:

metallicafan wrote:

Suppose the population of the country in current year is 1000.

So annual increase is 1000 + 39.4 - 19.4=1020

Hence every year there is an increase of 2%.

2000=1000(1+(2/100))^n

n=35 Answer is D. (But Calculation is somewhat tedious.) Anything simple than this?

Consider KUDOS if its helpful.

Yes, I also solved it in that way. The problem is that you cannot use a scientific calculator during the exam LOL.

I think we need the help of the moderators!

Can anyone guide me how to solve this manually.I don't have any clue.

2000=1000(1+(2/100))^n

You cannot solve it manually. You need a calculator to do it.

Though, when the amount is twice the principal, we have a simple formula (which will be given in the question if this question comes in GMAT)

The principal doubles in 70/r years.

Since the rate of interest is 2% here, and the principal doubles from 1000 to 2000, the number of years it will take is 70/2 = 35 years.[/quote]

Thanks a lot Karishma.I usually get struck on this last part in these kind of questions.