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**keeg** E.Coli exponential growth problem, what am i doing wrong?

Okay, so I have found the correct formula for this problem, but for some reason I must be doing something wrong, because I can't get the right answer. Here is the Original Problem, and I will go through what I did:

A common inhabitant of human intestines is the bacterium Escherichia coli. A cell of this bacterium in a nutrient-broth medium divides into two cells every 20 minutes. **The initial population of a culture is 55 cells.**

a) find relative growth rate. k= 2.08 (thats right)

b) Find an expression for the number of cells after t hours. = P(t)=55e^(2.08t) (this is right)

now, for c) it asks: Find the number of cells after 5 hours

________ billion cells. however, the number I am getting by just plugging it into the calculator, is 1807279.412. So i divided it by 1000, and said that it is 1807.279 billion. But Is this wrong?

Also, how do I find the rate of growth after 5 hours?

I feel like I must be doing something kind of stupid, because it seems smile enough. Thanks!