Fifteen person, among whom are $A$ and $B$ , sit down at random at a round table. It $p$ is the probability that there are exactly $4$ persons between $A$ and $B$ find $7 p$

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Solution

Let $A$ occupy any seat at the round table. Then there are $14$ seats available for $B$ . If there are to be four persons between $A$ and $B$ , then $B$ has only two ways to sit, as shown in fig. Thus, the probability of the required event is $2 / 14 = 1 / 7$ .

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Fifteen person, among whom are A and B, sit down at random at a round table. It p is the probability that there are exactly 4 persons between A and B find 7p

Let A occupy any seat at the round table. Then there are 14 seats available for B. If there are to be four persons between A and B, then B has only two ways to sit, as shown in fig. Thus, the probability of the required event is 2/14=1/7.

Fifteen person, among whom are $A$ and $B$ , sit down at random at a round table. It $p$ is the probability that there are exactly $4$ persons between $A$ and $B$ find $7 p$

Let $A$ occupy any seat at the round table. Then there are $14$ seats available for $B$ . If there are to be four persons between $A$ and $B$ , then $B$ has only two ways to sit, as shown in fig. Thus, the probability of the required event is $2 / 14 = 1 / 7$ .