Dr. Kevin Callahan has asked his students to prepare a sample containing 22 mill

Question

Dr. Kevin Callahan has asked his students to prepare a sample containing 22 million e-coli bacteria by 2pm on Thursday to be used for the lab. It can be done by seeding 100 cells in a Petri dish. The number of cells doubles every 20 min, so it takes about 6hrs to grow the required number of cells .Students were asked to come to the lab by 8am on Thursday morning to prepare e-coli sample. A pair of students have decided that they could cut time in half by seeding the Petri dish with 200 cells, instead How much time would they save by doing so? At what time would they have to start to have it done by 2pm?

Explanation / Answer

Given that, generation time for bacteria = 20 min.

and it takes 6 hr to reach 22*106million cells in petri plates, when itnitial no of cell = 100.

To reduce the time, they seeded with 200 cells initially. By doing this they can only reduce 20 minutes from 6hr i.e. 5:40 hr time required to get 22million cells, and decrease number of generation by one. Therefore, they have to start at 8:08 AM to have it done by 2pm.

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