Question 1080159: In an attempt to determine the number of $20 bills in active circulation a bank marked 300 bills with an invisible ink. The bills were then released to the public. In a sample of 1000 bills taken six weeks later, 34 had the invisible mark. Estimate the number of $20 bills in circulation in this area.
HINT: Use the expected value formula.
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! not exactly sure if this is correct, but .....
300 bills were marked.
out of a sample of 1000, 34 were marked.
the ratio of marked bills to sample bills is 34/1000 = .034
if that same ratio applies to the population, and you let x represent the population, then you get:
.034 * x = 300
this says that 300 bills represents .034 of the population.
solve for x to get x = 300 / .034 = 8823.529412.
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