Answer:
3 hours
Step-by-step explanation:
i made a chart of how many there should be after each 20 minute period wchich had 12 answers. every three groups of bacteria equals one hour. the bacteria count of 2,560 was on the ninth mark, meaning that it was on the third hour seeing as groups 1-3 are hour one, groups 4-6 are hour two, groups 7-9 are on hour three, and groups 10-12 aer on hour 4. group nine makes hour three complete, so there is your answer. hope this doesnt seem like a bunch of nonesense words.
