Question 1133179: A certain plant reproduces by splitting into equal-sized halves every 30 minutes. In 30 minutes, each of these new plants grows sufficiently to reproduce once again.
A gardener plants one of these plants in the centre of a circular plot, and finds it takes eight hours to cover the plot. If he had commenced with two plants rather than one in the same plot, the time taken to cover the plot would have been
A 4 hours
B 4.5 hours
C 7.5 hours
D 8 hours
Answer by greenestamps(13198)   (Show Source):
You can put this solution on YOUR website!
By logical reasoning, answer C, 7.5 hours.
In the given scenario, starting with one plant filled the garden in 8 hours, with the number of plants doubling every 30 minutes.
But 30 minutes after the gardener planted the first plant there were 2 plants; and from there the time it took to fill the garden was 30 minutes less than 8 hours, or 7.5 hours.
So if he had started with 2 plants, it would have taken the same 7.5 hours to fill the garden.
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