SOLUTION: There are n balls in a box, each marked with a unique number from 1 to n. k balls are selected randomly from the box, and then returned to the box. What is the probability that the
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Question 1200619: There are n balls in a box, each marked with a unique number from 1 to n. k balls are selected randomly from the box, and then returned to the box. What is the probability that the numbers on the selected balls satisfy the condition X1 < X2 < ... < Xk? Consider the case where n=20 and k=5. Answer by ikleyn(52904) (Show Source):
Five numbers can be ordered in 5! = 5*4*3*2*1 = 120 different ways.
Of these 120 different ordering, only one ordering is ascending order.
Therefore, the probability to get an ascending order is .
