ANSWER
[tex]r(n)\text{ = 1000}\times(\frac{2}{5})^n[/tex]STEP-BY-STEP EXPLANATION:
Given information
The tortoise travels three-fifths of the remaining distance to the ocean
The initial distance of tortoise from the ocean = 1000 ft
Step 1: Determine the remaining distance at the end of each day
Let x represents the remaining distance at the end of each day
[tex]\begin{gathered} x\text{ = 1 - }\frac{3}{5} \\ x\text{ = }\frac{\text{ 5 - 3}}{5} \\ x\text{ = }\frac{2}{5} \end{gathered}[/tex]Hence, the remaining distance at the end of each day is two-fifths (2/5)
So, the function can be modeled by an exponential with a growth factor of 2/5
Hence, the modeled equation can be written below as
[tex]\begin{gathered} r(n)\text{ = }1000\times\text{ (}\frac{2}{5})^n \\ \text{Where} \\ r(n)\text{ = number of remaining distance (feet) after n days travels} \\ n\text{ = number of days} \end{gathered}[/tex]