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We have a pond containing a single bacterium. The number of bacteria double every 5 minutes, and the pond is full of them in 24 hours. If we started with the same pond but two bacteria, how long will it take to fill the pond?

Tags:logic, algorithm, math

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4 Answers


I struggled with this a bit and got close. I believe answer is: 23:55

Anonymous on


The first pond started with 1 bacterium and doubled to 2 in five minutes. Therefore, the second pond will take 5 minutes less than the first to be full. ie: 23:55

Joe on


This is a clear case of Geometric progression. Find the nth term Tn1 = a*r^(n-1). where n = (24 * 60)/5,a = 1 and r=2. when the initial value (a) = 2, the values become n = ?, a = 2 and r = 2. Since Tn1 = Tn2, Equate the RHS of both the equation. Since the base are equal, equate the powers, doing so will give the n value. When n is convert into minutes one get 23 hrs 55 minutes.

Prabhakar on


this is easy, you don't need all the math. The pond was half full five minutes before, so it's 23:55

scott on

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