Calculation :
It is given that in the start there are 5 bacteria and it keeps doubling after every 20 minutes we have to find the number of bacteria after 4 hours
4 hours = 240 minutes
⇒ Number of times the bacteria have doubled = 240÷20 = 12 times
It means the bacteria have doubled by 12 times
⇒Total bacteria = 5×2¹²= 20480
The time when there will be 2560 bacteria
⇒ the bacteria had doubled 9 times to reach the mark of 2560
so total time = 9 ×20= 180 minutes = 3 hours
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Question: There are 5 bacteria in a Petri dish at the start of the experiment. This type of bacteria doubles every 20 minutes