Growth of Bacteria in a Culture
Suppose the rate of growth of bacteria in a Petri dish is given by q(t) = 3t, where t is given in hours and q(t) is given in thousands of bacteria per hour. If a culture starts with 10,000 bacteria, find the function Q(t) that gives the number of bacteria in the Petri dish at any time. How many bacteria are in the dish after 2 hours?
Solution: We have
Q(t) = ∫3t dt = 1.5t^2 + C. Then, at t = 0 we have Q(0) = 0 + C = 10, so C = 10. Therefore, we get Q(t) = 1.5t^2 + 10. At time t = 2, we have
Q(2) = 1.5(2)^2 + 10 = 16. After 2 hours, there are 16,000 bacteria in the dish.
1.35 From Example 1.42, suppose the bacteria grow at a rate of q(t) = 2t. Assume the culture still starts with 10,000 bacteria. Find Q(t). How many bacteria are in the dish after 3 hours?