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

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(52908) (Show Source): You can put this solution on YOUR website!
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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  .

Solved.

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