For this case we have the following function: n (t) = 2400 * (5) ^ t For n (t) = 60000 we have: 60000 = 2400 * (5) ^ t We clear the value of t. For this we use the logarithm: (5) ^ t = 60000/2400 log5 ((5) ^ t) = log5 (60000/2400) t = log5 (60000/2400) t = 2 days Answer: the number of bacteria in the culture will be 60 comma 000 after: t = 2 days