<PRE><B>Question 1147953</B>
If the pollution of Lake Erie were stopped suddenly, it has been estimated that the level y of pollutants would decrease according to the formula 
y = y0e−0.3821t, where t is the time in years and y0 is the pollutant level at which further pollution ceased. How many years would it take to clear 60% of the pollutants?
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60% clear ---&gt; 40% remaining = 0.4
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{{{0.4 = 1*e^(-0.3281t)}}}
{{{-0.3281t = ln(0.4)}}}
t =~ 2.7927 years


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