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Interview Question


If you and your four friends go out to dinner and are

  seated at a round table with five seats, what is the probability you will sit in exactly the correct order with respect to your ages. Assume no one is the exact same age.

Interview Answer

3 Answers


distribution would indicate there are 116 different combinations. But they are primarily interested with the method you used to reach this conclusion.

Interview Candidate on Apr 27, 2012

There are 5 seats available. I'm assuming it doesn't matter if the order is CW or CCW. Pick the oldest person it doesn't matter where he sits. There's a 50-50 chance the youngest person takes 2/4 of the remaining seats next to the oldest person. That determines the direction of the table. There's a 1/3 chance the next oldest sits next to the youngest, 1/2 chance the 3rd oldest sits next to them, and a 100% chance the 2nd oldest takes the final seat. So 1*(2/4)*(1/3)*(1/2)*1= 1/12

Kevin on May 13, 2012

if right or left arrangement doesnt matter (1/4!)*2 and if it does just (1/4!). The reason you pick 4 is because it does not matter who the first person is, only the ensuing order of people.

Anon on Aug 11, 2013

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