An amoeba propagates by simple division; each split takes three minutes to complete. When such an amoeba is put into a glass container with a nutrient fluid, the container is full of amoebas in one hour.
How long would it take for the container to be filled if we start with not one amoeba, but two?
(In reply to Puzzle Solution
by K Sengupta)
Proceeding in a similar manner, we observe that if there were 2^n amoebas to start with, where n is a positive integer < 20, then it would take precisely (60-3*n) minutes to fill the container.