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Population growth of animal species (math word problem, already partially solved)?

The population growth of an animal species is described by F(t)=400 log (2t + 4) where t is measured in months. a) find population of species after 6 months. b) how many month until population doubles?

I've done a and gotten these results

a) F(6)=400 log (2(6) +4) = 482 months

As for b, this is my interpretation of how I should solve, but I'm not sure.

b) 482*2= 964

964 = 400 log (2t +4)

964/400 = log (2t +4)

2.41 = log (2t +4)

I'm not sure if I'm doing it correctly or if I am correct, where I should go from there.

1 Answer

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  • ?
    Lv 5
    7 years ago

    Your answer for part a) should be 482 individuals (NOT months)

    As for b) your math is good, just continue on with:

    10^2.41 = 2t + 4

    257 = 2t +4

    253 = 2t

    126.5 months = t

    but this answer is for number of months AFTER the initial 6 months of population growth. I think that the question is asking how long it takes the INITIAL population to double, in which case we need to find the population at time zero.

    F(0) = 400 * log 4

    = 400 * 0.60206 or approx. 241 individuals

    then double this to get 482, which is exactly the number you got for six months of population growth.

    Lets check:

    482 = 400 (log 2t + 4)

    1.205 = log (2t + 4)

    10^1.205 = 2t + 4

    16 = 2t + 4

    12 = 2t

    t = 6 months!

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