a. To find the number of trout in 2.5 months, we can substitute n = 2.5 into the given equation:
T = 1800 (1.15)^n
T = 1800 (1.15)^2.5
T ≈ 2708.67
Therefore, there will be approximately 2,709 trout in the lake after 2.5 months.
b. To find the number of trout 2 months before the season opened, we need to use a negative value of n that represents the time before the start of the trout season. If we assume that the start of the season is month 0, then 2 months before the start of the season would be month -2. Thus, we can substitute n = -2 into the given equation:
T = 1800 (1.15)^n
T = 1800 (1.15)^(-2)
T ≈ 980.92
Therefore, there were approximately 981 trout in the lake 2 months before the start of the trout season.