Question

a lake is stuck with 1,550 young carp. the number of the original fish alive after t years is given by the function P (t)= 1550e^-0.4t, when will there be 440 of the original fish left from to the nearest tenth

Answer 1

`\begin{gathered} 440=1550e^(-0.4t)\rightarrow \\ e^(-0.4t)=(440)/(1550) \\ -0.4t=\ln ((44)/(155))\approx-1.26 \\ t=(1.26)/(0.4)\approx3.14\approx3.1 \end{gathered}`

so the time needed is 3.1 years