On her vacations Veena visits four cities `(A , B , C a n d D)`in a random order. What is the probability that she visits(i) A before B?(ii) A before B and B before C?(iii) A first and B last?(iv) A either first or second?(v) A just be

Explanation

Here, sample space will contain `4!` ways.

`S = `

`{ABCD,ACBD,ABDC,ADBC,ACDB,ADCB,`

`BACD,BADC,BCAD,BCDA,BDAC,BDCA,`

`CABD,CADB,CBAD,CBDA,CDAB,CDBA,`

`DABC,DACB,DBAC,DBCA,DCAB,DCBA}`

So, `n(s) = 24`

(i)Number of ways Veena travels A before B `= 12`

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