Given data:
The given growth rate is r=7.8%=0.078.
The final number of bacteias in terms of initial is P'=2P.
The expression for the bacterias growth rate is,
[tex]P^{\prime}=P(1+r)^t[/tex]
Substitute the given values in the above expression.
[tex]\begin{gathered} 2P=P(1+0.078)^t \\ 2=(1.078)^t \\ \ln (2)=t\ln (1.078) \\ t=\frac{\ln(2)}{\ln(1.078)} \\ =9.23\text{ hours} \end{gathered}[/tex]
Thus, after 9.23 hours population of the bacterias doubled.
