This is an example of exponential growth.
Since the population doubles in size every 29 hours,
and the initial population is 30000,
then in 29 hours,
the population = 30000 x 2 = 60000
and in
another 29 hours (total of 58 hours from the start),
the population = 60000 x 2 = 120000
Hence the population after 58 hours is 120000 bacteria.
