The given trend for the bacteria population is a geometric sequence with initial amount of 8 (a0) and the common ratio equal to 3. The amount of bacteria at any time t is,
at = (a0) x r^(t - 0)
Substituting the given,
at = (8) x 3^(4 - 0)
The numerical value for at is 648. Thus, there will be 648 bacteria after 4 weeks.
