The contents of a tanker truck carrying a liquid organic waste are spilled accidentally into a small lake. The resulting initial concentration of the waste in the lake is 300 mg/1. The volume of the lake is 105 m³. A stream that flows into and out of the lake has a flow rate of 1200 m³/d. If the organic waste in solution undergoes first-order photochemical decay (r = kC) with a k value of 0.008 d-1, determine the time required for the concentration of the waste in the lake to be reduced to 10 percent of the initial value.

The radioactivity of an element decreases by 72 percent in 820 days. (a) Determine the half-life of the element, rounded to a whole number: (b) Determine the number of days, rounded to a whole number, for a sample of 100 mg to decay to 61 mg:

How long will it take a population of bacteria to reach a certain size, given that we know its growth rote?

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