1. ## Fish population problem.

A large pond is stocked with fish. The fish population P is modeled by the formula P = 3t + 10t + 120, where t is the number of days since the fish were first introduced into the pond. How many days will it take for the fish population to reach 500?

2. ## fish

Ok, so the population wanted is 500. We plug in and now we have:

500
= 3t + 10t + 120, solve for t

I suggest bringing the 3t and then 120 to the left side with subtraction then squaring both sides as your first few steps to solving for t.

3. Originally Posted by tmac11522
A large pond is stocked with fish. The fish population P is modeled by the formula P = 3t + 10t + 120, where t is the number of days since the fish were first introduced into the pond. How many days will it take for the fish population to reach 500?
$500 = 3t + 10\sqrt{t} + 120$

$0 = 3t + 10\sqrt{t} - 380$

let $u = \sqrt{t}$ ...

$0 = 3u^2 + 10u - 380$

$u = \frac{-10 \pm \sqrt{100 - 4(3)(-380)}}{6}$

taking the positive solution ...

$u \approx 9.7107$ ...

$t = u^2 \approx 94.3$ days

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### the population of fish in a local bay is modeled by the equation

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