Answer:
There will be 50 bacteria remaining after 28 minutes.
Explanation:
The exponential decay equation is

N= Number of bacteria after t minutes.
= Initial number of bacteria when t=0.
r= Rate of decay per minute
t= time is in minute.
The sample begins with 500 bacteria and after 11 minutes there are 200 bacteria.
N=200
= 500
t=11 minutes
r=?



Taking ln both sides



To find the time when there will be 50 bacteria remaining, we plug N=50,
= 500 and
in exponential decay equation.


Taking ln both sides




minutes
There will be 50 bacteria remaining after 28 minutes.