Question 1102063
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<pre>
Mathematically, the question is:  at which t the quantity


N = 330/(1+10(0.81)^t) = {{{330/(1+10(0.81)^t)}}}


will reach the value of 80.


I will show the plot first



{{{graph( 330, 330, -1.5, 10.5, -20.5, 120.5,
          330/(1+10(0.81)^x)
)}}}


Plot y = {{{330/(1+10(0.81)^t)}}}



Next, I will show the table


Year, t    N = 330/(1+10(0.81)^t

  0	       30.00
  1	       36.26
  2	       43.65
  3	       52.26
  4	       62.21
  5	       73.55
  6	       86.29


From the plot and from the table you can see that the number N increases monotonically and will exceed the value of 80 in 6 years.
</pre>

<U>Answer</U>. &nbsp;How many years must a protection program be maintained for the fish population?  &nbsp;&nbsp;- &nbsp;6 years.