If each year the population of the country grows by 20%, how many years will elapse before the population of the country doubles?

a) 3 b) 4 c)5 d) 6 e) 7.

I need a clarification in this question.

By solving, the population is doubled in the 4th year. But the question is " HOw many years will elapse before the population doubles?". Hence, i chose the option (a), which is "3". But the OA is option b.

Where am i going wrong?. Is my understanding of this question incorrect?.

Please help.

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