SOLUTION: I get the general idea on how to set up the problems, but when I tried to solve it apparently it was wrong so I don't have a clue, please help thank you. The count in a bac

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: I get the general idea on how to set up the problems, but when I tried to solve it apparently it was wrong so I don't have a clue, please help thank you. The count in a bac      Log On


   

Question 1193863: I get the general idea on how to set up the problems, but when I tried to solve it apparently it was wrong so I don't have a clue, please help thank you.


The count in a bacteria culture was 100 after 15 minutes and 1800 after 30 minutes. Assuming the count grows exponentially,
What was the initial size of the culture?
Find the doubling period.
Find the population after 120 minutes.
When will the population reach 10000?
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Two points for an exponential function, (15,100) and (30,1800)

y=ab%5Ex


Use the points:
system%28100=ab%5E15%2C1800=ab%5E30%29
1800%2F100=%28ab%5E30%29%2F%28ab%5E15%29
18=b%5E15
b=18%5E%281%2F15%29
b=1.2125
Using the first equation
ab%5E15=100
a=100%2F%28b%5E15%29
a=100%2F%281.2125%5E15%29
a=5.5561

The function as y=5.5561%2A1.2125%5Ex
but this method may be not the best.
(Note that the initial bacteria count cannot be between two whole values.)