Let the population of rabbits surviving at a time t be governed by the differential equation d p t d t = 1 2…

Let the population of rabbits surviving at a time t be governed by the differential equation dptdt=12{pt-400}. If p(0)=100, then p(t) equals 
  1. 600 - 500 et2
  2. 400-300 e-t2
  3. 400 - 300 et/2
  4. 300-200 e-t2

Solution

dptdt=12{pt-400}

p0=100

2dptpt-400=dt

Integrating,

0p(t)dp(t)pt-400=0t12dtlnpt-4000pt=t2

lnpt-400300=t2

pt-400=300et2

400-pt=300et2    (pt<400)

pt=400-300et2

Asked in: JEE Main 2014 (06 Apr)

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