Jeff Miller

GMAT OFFICIAL GUIDE PS – At the start of an experiment, a certain population consisted of 3 animals…

At the start of an experiment, a certain population consisted of 3 animals…

Solution:

We are starting with 3 animals, and at the end of each month that number of animals doubles in size. Thus, we can say:

starting number of animals = 3

number of animals at the end of month 1 = 3 x 2 = 3 x 2^1

number of animals at the end of month 2 = 3 x 2 x 2 = 3 x 2^2

number of animals at the end of month 3 = 3 x 2 x 2 x 2 = 3 x 2^3

Notice that the exponent attached to the base of 2 corresponds with the month number. Thus, after 10 months there will be 3 x 2^10 animals.

Answer: D

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