There are several information's of immense importance already given in the question. Based on those information's the answer can be easily deduced.
Initial number of bacteria in the culture = 1000
Number of bacteria after t hours = 1000 (2)^t
Then
1000 (2)^t = 50000
2 ^t = 50
t = 5.6
I hope the procedure is clear enough for you to understand.
A bad line measurement (aka control) is set up so that you can compare your results from each test against so it gives the values a meaning as it shows how they differ from eachother
What are you trying to find? That is a pedigree
