A dice is thrown twice and the sum of the numbers appearing is observed to be 6. What is the conditional probability that the number 4 has appeared at least once?

Explanation

A= sum of the numbers
appearing on two dice is `6`

`(1,5),(5,1),(2,4),(4,2),(3,3)`


`n(A)=5`



B= number `4` has appeared at least once

`(1,4),(4,1),(2,4),(4,2),(3,4),`
`(4,3),(4,4),(4,5),(5,4),(4,6),(6,4)`

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