A pair of dice is thrown. Find the probability of getting 7 as the sum of it is known that hte second die always exhibits a prime number.

Explanation

Let below are the two given events,

`A = `A prime number appears on second die.

There are `3` numbers `(2,4,6)` that are prime between `1` and `6`.

So, second die can contain any of these three numnbers.

First die can have any of he `6` numbers.

`:. n(A) = 6*3 = 18`

Let `B = `Event that sum of both dice is `7`.

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

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