Aparticular strain of bacteria triples in population every 15 minutes. assuming you start with 120 bacteria in a petri dish, how many bacteria will there be in 1 hour

60 minutes in an hour. 4 sets of 15 in 1 hour. 120 times 3 is 360. That's 1 set of 15 minutes. 360 times 3 is 1080. That's the second set of 15 minutes. 1080 times 3 is 3240. That's the third set of 15 minutes. 3240 times 3 is 9720. That's the 4th set of 15 minutes. 9720 is the amount of bacteria that will be in your Petri dish at the end of 1 hour.

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