From a pack of 9 cards numbered 1,2,3.......9 , three cards are drawn at random and laid on a table from left to right. What is the probability that the digits are drawn in descending order (by just using permutation)?

1 Answer
Oct 15, 2017

The probability is 1/6.

Explanation:

There are ""_9P_3=9*8*7=504 possible selections to lay three cards from left to right.

However, there are only ""_9C_3=(""_9P_3)/(""_3P_3")=(9*8*7)/(3*2*1)=84 possible selections.

The reason this is ""_9C_3 is because for every selection of three different cards, there is only one possible way for it to be in descending order.

to lay the three cards in descending order. Therefore, the possibility is 84/504=1/6.