A probability problem by Samina Siamwalla
Probability
Level
2
The number of ways in which 8 persons numbered 1,2,.....,8 can be seated in a ring so that 1 always sits between 2 and 3 is
240
72
120
360
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1 solution
1 always sits between 2 and 3 so it has a fix place
2 and 3 can arrange themselves in 2 ways
And remaining 5 people can arrange themselves in 5! ways
So total number of ways 8 people can arrange themselves is 240