Probability

 

My sock drawer contains two red socks, two white socks, and two blue socks.  For three days in a row, I pull out two socks out of my sock drawer at random.  What is the probability that I get matching socks on all three days?      

 

The first sock can be anything                                prob  1 / 1     

Probability second sock matches                            prob  1 / 5     

The third sock can be anything                                prob  1 / 1     

Probability fourth sock matches                                prob  1 / 3     

If the above happens, all that's left is the last pair     prob  1 / 1     

 

To find the probability of every condition listed above     

happening, multiply individual probabilities together.     1 • (1/5) • 1 • (1/3) • 1  =  1 / 15     

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