A pear of dice is thrown. Find the probability of getting 7 as the sum, if it is known that the second die always exhibits an odd number.

Explanation

A= represents second die shows odd number


B= represents sum of the numbers on two dice is 7 .

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A={(1,1),(1,3),(1,5),(2,1),(2,3),(2,5),(3,1),(3,3),(3,5),(4,1),(4,3),(4,5),(5,1),(5,3),(5,5),(6,1),(6,3),(6,5)}`

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B={(2,5),(5,2),(3,4),(4,3),(1,6),(6,1)}`


Then ,

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A cap B={(2,5),(4,3),(6,1)}`

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therefore P(B / A)=frac{n(A cap B)}{n(A)}=frac{3}{18}=frac{1}{6}`