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A chalk box contains 5 pink chalks and 4 white chalks. If three items are picked at random, assuming that you return the chalk after picking each time, what is the probability that at least 1 of them is a pink chalk? *

91.22%

76.38%

19.83%

10.97%

 Apr 7, 2022
 #1
avatar+23183 
+1

If you have no other way of approaching this problem, you can do it by listing all the possibilities:

 

PWW  =  (5/9)(4/9)(4/9)  =  ...

WPW  =  (4/9)(5/9)(4/9)  =  ...

WWP  =  (4/9)(4/9)(5/9)  =  ...

 

PPW  =  (5/9)(5/9)(4/9)  =  ...

PWP  =  (5/9)(4/9)(5/9)  =  ...

WPP  =  (4/9)(5/9)(5/9)  =  ...

 

PPP  =  (5/9)(5/9)(5/9)  =  ...

 

and adding all the results together.

 

This can also be done by using combinations but, if you forget the 'easy' way, don't give up!

 Apr 8, 2022

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