Question
In a culture, the bacteria count is 1,00,000. The number is increased by 10% in 2 hours. In how many hours will the count reach 2,00,000, if the rate of growth of bacteria is proportional to the number present?
Solution
Let y denote the bacteria at any time t.
From the given condition,
where k is the constant of proportionality.
Separting the variables and integrating, we get,

...(1)
Let
be bacteria at time t = 0

Now,

...(3)
Let the bacteria be 2,00,000 from 1,00,000 in
hours
i.e.

From the given condition,

Separting the variables and integrating, we get,


Let


Now,



Let the bacteria be 2,00,000 from 1,00,000 in

i.e.


