Stewart – Calculus 8e ET Chapter 3 Form E
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____ 16. Let C (t) be the total value of US currency (coins and banknotes) in circulation at time. The table
gives values of this function from 1980 to 2000, as of September 30, in billions of dollars.
Estimate the value of C (1990) . Select the correct answer.
t 1980 1985 1990 1995 2000
C(t) 129.9 568.6
Answers are in billions of dollars per year. Round your answer to two decimal places.
a.
b.
c.
d.
e.
17. The half-life of cesium-137 is 30 years. Suppose we have a -mg sample. Find the mass that
remains after years.
18. Strontium- has a half-life of days. A sample has a mass of mg initially. Find the mass
remaining after 42 days.
19. Gravel is being dumped from a conveyor belt at a rate of ft/min and its coarseness is such that
it forms a pile in the shape of a cone whose base diameter and height are always equal. How fast is
the height of the pile increasing when the pile is ft high? Round the result to the nearest
hundredth.
20. Find the derivative of the function.
= cosh2 (2t2 + 3)