8 cases?
Level
pending
Given 10 balls in a box where 4 are black and the other 6 are white. 4 balls are taken out randomly and the balls are not put back.
What is the possibility that the fourth ball taken out is black?
The answer is 0.4.
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1 solution
The balls taken out actually do not affect the possability of a black ball being taken out.
So the answer is 4/10=0.4