Question

From a pack of 9 cards numbered 1-9, 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?

Answer 1

Answer: 1/6
Explanation: Since we need to draw three cards from a pack of 9 and the digits require an order, then our sample space becomes: 9P3.
Now, we don't care about picking an order when picking three cards to analyse, as there is only 1 way in arranging the three cards in descending order.

Thus, we get:


`(^(9)C_3)/(^(9)P_3) = (1)/(6)`