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Biologists stocked a lake with 500 fish and estimated the carrying capacity (the

ID: 1949237 • Letter: B

Question

Biologists stocked a lake with 500 fish and estimated the carrying capacity (the maximal population for the fish of that species in that lake) to be 3500. The number of fish tripled in the first year.

(a) Assuming that the size of the fish population satisfies the logistic equation dP/dt = kP (1 - P/K ) determine the constant k, and then solve the equation to find an expression for the size of the population after t years.
k= ?
P(t)= ?

(b) How long will it take for the population to increase to 1750 (half of the carrying capacity) ? answer in years

Explanation / Answer

a) dP/dt = kP(1-P/N)

ln P - ln (3500 - P) = kt + C

P/(3500 - P) = Ce^(kt)

Put P = 500, t=0 so C=.167
Put P=1500,t=1, C=.167 so k=1.50

b) 1750/(3500-1750) = .167e^(1.5t)

  t=1.19 years