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 one year ago
A box contains nine $1 bills, eight $5 bills, two $10 bills, and four $20 bills. What is the expectation if one bill is selected?
 one year ago
A box contains nine $1 bills, eight $5 bills, two $10 bills, and four $20 bills. What is the expectation if one bill is selected?

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RitiBahl100
 one year ago
Best ResponseYou've already chosen the best response.0The first step to doing probability is to count the total number of bills in the box, which in this case is 9+8+2+4 which is 23. Since there are 9 $1 bills, it is 9 out of 23 which could also be written as 9/23 and there's you're answer.

zepdrix
 one year ago
Best ResponseYou've already chosen the best response.0the word ONE is not representative of the ONE dollar bills in this case, it means a "single" bill is selected.

zepdrix
 one year ago
Best ResponseYou've already chosen the best response.0But yah Riti has the right idea. So the total number of bills is 23. The expected value of the $1 bills we can represent this way, as Riti explained,\[\large $1\left(\frac{9}{23}\right)\]We'll add to that the value of each other bill as well. This will give us the value we should expect to gain from one bill selection.\[\large $1\left(\frac{9}{23}\right)+$5\left(\frac{8}{23}\right)+$10\left(\frac{2}{23}\right)+$20\left(\frac{4}{23}\right)\] Which ends up giving us an expectation of around $4.74 on a single bill selection.
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