- #1
tamintl
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Homework Statement
Four numbers are chosen independently at random, with replacement, from the set {1,2,3,4,5,6,7,8,9,10}
Let A be the event that the four numbers are distinct.
Let B be the event that exactly two of them are even.
Calculate P(A) and P(B)
Homework Equations
The Attempt at a Solution
This is easy but I don't know why I am getting the worng answer..
P(A) = (10C1).(9C1).(8C1).(7C1) / (10C1).(10C1).(10C1).(10C1) = 5040/10000 = 0.504 THIS IS CORRECT...
Now for the dodgy one. My attempt:
P(B) = (5C1).(5C1).(5C1).(5C1) / (10C1).(10C1).(10C1).(10C1) = 1/16 = 0.0625
I have the solution and it tells me that P(B) is wrong.. I know what I have missed out but I feel I have done everything needed.
The actual solution is: (4C2).(5C1).(5C1).(5C1).(5C1) / (10C1).(10C1).(10C1).(10C1) = ...
Thanks for any help!