Suppose that a bacteria colony has an initial population of 2669 organisms, and after 27 hours, the colony has 6476 organisms… What will the population be after 42 hours?
Essentially you need to work out the rate at which the colony is multiplying. Or, how much does it increase from the population at 0 hours to the population at 27 hours, and how much does it increase each hour.
To work that out you do (6476 - 2669), which is the number of bacteria created in 27 hours, then you divide the answer (3807) by 27, which is 141, the number of bacteria in one hour.
Then you reorder the equation. 141 (number of new bacteria every hour) multiplied by 42 (the number of hours) added to the original number of bacteria.
This equals 8591