A culture of a certain bacteria is known to double in number every 3 hr. If the culture has an initial count of 15, what will be the population of the culture at the end of 18 hr?
A) 958 bacteria
B) 959 bacteria
C) 960 bacteria
D) 477 bacteria
E) 480 bacteria

Question

Quizplus · Accepted Answer

Since the population doubles every 3 hours, at the end of 18 hours, the population would have doubled 6 times (18/3=6).

Starting with 15 bacteria, after the first 3 hours, the population would be 30 (15 x 2^1). After the second 3 hours, the population would be 60 (15 x 2^2). After the third 3 hours, the population would be 120 (15 x 2^3). After the fourth 3 hours, the population would be 240 (15 x 2^4). After the fifth 3 hours, the population would be 480 (15 x 2^5). And after the sixth 3 hours, the population would be 960 (15 x 2^6).

Therefore, at the end of 18 hours, the population of the culture would be 960 bacteria.

A Culture of a Certain Bacteria Is Known to Double