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%
+23245 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!
