A strain of bacteria reproduces at the rate of 25% every 12 min. In how much time will it triple itself?

Correct answer marked below

96 min

72 min

60 min

Correct

48 min

40 min

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Explanation

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Official Explanation

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The bacteria grows at 25% every 12 minutes.

Let the initial quantity be 1.

After each 12‑minute period, the quantity is multiplied by

1.25

.

We want the time when the quantity becomes 3.

So we solve:

1.25^x = 3

1.25^4 = (1.25^2)^2 = (1.5625)^2 \approx 2.44

…

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What this question tests

Your ability to apply GMAT math concepts to solve a multi-step problem quickly and accurately. At the 705-805 level, accuracy and speed both matter.

Overcomplicating the setup — most GMAT problems reward a direct, organized approach over brute calculation.