Question 1
From a group of 9 people, you randomly select 4 of them.
What is the probability that they are the 4 oldest people in the group?
Give your answer as a fraction
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Step 1 ：The problem is asking for the probability of a specific event happening. In this case, the event is selecting the 4 oldest people from a group of 9.

Step 2 ：The total number of ways to select 4 people from a group of 9 is given by the combination formula \(C(n, k) = \frac{n!}{k!(n-k)!}\), where n is the total number of items, k is the number of items to choose, and ! denotes factorial.

Step 3 ：The event we are interested in (selecting the 4 oldest people) can happen in only one way.

Step 4 ：So, the probability of this event is the number of ways the event can happen divided by the total number of possible events.

Step 5 ：Total number of ways to select 4 people from a group of 9 is 126.

Step 6 ：Number of ways the event can happen is 1.

Step 7 ：Probability = \(\frac{1}{126}\)

Step 8 ：Final Answer: The probability that the 4 oldest people are selected from the group is \(\boxed{\frac{1}{126}}\).