SOLUTION: Three cards are drawn from a deck without replacement. The number of aces is counted. The expected value of the random variable in the experiment is: A. 1 B. 1.0134 C. .2308

Algebra.Com
Question 169548: Three cards are drawn from a deck without replacement. The number of aces is counted. The expected value of the random variable in the experiment is:
A. 1
B. 1.0134
C. .2308
D. .2174
E. None of the above

Answer by Edwin McCravy(20055)   (Show Source): You can put this solution on YOUR website!

X = no. of aces drawn which can either be 0, 1, 2, or 3.

So make this chart:



Now we must calculate the probabilities to go in
the bottom row of the chart.

We first calculate the probability of getting 0 aces.
This means we draw 3 non-aces.  There are 48 non-aces.
So the number of ways to choose three non-aces is


The denominator is 

So the probability of getting 0 aces is 

Next we calculate the probability of getting 1 ace.
This means we draw 2 non-aces and 1 ace. There are 
48 non-aces. So the number of ways to choose two 
non-aces is  and the number of ways to
choose the ace is  ways.  That's 
 ways.

The denominator again is 

So the probability of getting exactly 1 ace is 


Next we calculate the probability of getting 
exactly 2 aces. This means we draw 1 non-ace and 
2 ace3. There are 48 non-aces. So the number of 
ways to choose one non-aces is  and 
the number of ways to choose 2 aces is  
ways.  That's 
 ways.

The denominator is as before 

So the probability of getting exactly 2 aces is 


Finally we calculate the probability of getting 3 aces.
The number of ways to choose 3 aces is  ways.  

The denominator is 

So the probability of getting exactly 3 aces is 


So we fill in the chart:

 

Now to find the expectation, we add the products of each
value of x times its probability:



That rounds to choice C, 

Edwin

RELATED QUESTIONS

Find the expected value of the random variable in the experiment. Three cards are drawn... (answered by stanbon)
Five cards are drawn from a deck without replacement. The number of aces is counted. Find (answered by stanbon)
What is the probability of drawing three aces from a deck of cards if three cards are... (answered by stanbon)
what is the probility of getting four consecutive aces when four cards are drawn without... (answered by drk)
Three cards are drawn from an ordinary deck without replacement what is the probability... (answered by Boreal)
four cards are selected, one at a time from a standard deck of 52 cards. Let x represent (answered by richard1234)
three cards are drawn in succession from a deck without replacement. Find the probability (answered by stanbon)
Three cards are drawn in succession from a deck without replacement. find the probaility... (answered by Fombitz)
find the probability of getting four consecutive aces when four cards are drawn without... (answered by checkley77)