Solve the problem.How long will it take a sample of radioactive substance to decay to half of its original amount, if it decays according to the function A(t) = 400e-0.247t, where t is the time in years? Round to the nearest hundredth of a year.
A. 27.06 yr
B. 24.26 yr
C. 98.80 yr
D. 2.81 yr
Answer: D
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Use a trigonometric substitution to evaluate the integral.
A. 
ln ( 1 + 4 ln2x) + C
B. 
tan-1 (2 ln x) + C
C. 
tan-1 (4 ln2 x) + C
D. 
tan-1 (2 ln x) + C
Solve the problem.A 100 gal tank is half full of distilled water. At time = 0, a solution containing 2 lb/gal of concentrate enters the tank at the rate of 4 gal/min, and the well-stirred mixture is withdrawn at the rate of 
When the tank is full, how many pounds of concentrate will it contain?
A. 200 pounds B. 150 pounds C. 187.5 pounds D. 175 pounds
Convert the radian measure to degree measure. Use the value of ? found on a calculator and round answers to two decimal places.-1.5733
A. -90.84° B. -89.64° C. -89.14° D. -90.14°
Determine how many of the first 5 statements in the sequence obtainable from the given statement are true.The measure of each exterior angle of a regular polygon with n sides is 
. (n ? 3)
A. 4 B. 3 C. 5 D. 2