[Math] the probablity of sitting next to the friend

probability

Let's say you are at a table with $5$ others, everyone is seated randomly around a $6$ person table, and you only know $1$ person at this party.

  1. What is the likelihood you sit next to the individual that you know?
  2. What is the likelihood you are seated opposite to the person that you know?
  3. What is the likelihood that you sit next to two strangers?

The table has $6$ seats so if you sit in any one seat then there are $5$ chairs left over. Since your friend can be seated on either side of you that leaves 3 chairs. With that reasoning would it be $1/3$ ($2/6$)?

Best Answer

The answer to #1 is not $\frac26$ but $\frac25$, since you can consider your own seat fixed without loss of generality, leaving 5 chairs, two of which are adjacent to you. Similarly, the answers for #2 and #3 are $\frac15$ and $\frac35$ respectively, both obtained by counting the number of chairs where the desired result is obtained by your friend sitting there by the number of empty chairs.

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