Two groups A and B wrote an exam The probability of A 39 s pass is 2 7 and the probability of B 39 s...........

Explanation:

Let A be the event of the group A pass
Let B be the event of the group B pass

Then, A'= Event of the group A's fail and B'= event of the group B's fail.

Therefore, p(A) = 2/7 and p(B) = 2/5,
P(A') = 1 - P(A) = 1- 2/7 = 5/7 and P(B') = 1- P(B) = 1- 1/5 = 4/5

Required probability = P[( A And B') Or (B And A')]
= P[( A And B') Or (B And A')]
= P[( A And B') + (B And A')]
= P[( A And B')] + p[(B And A')]
= p(A) x p(B') + P(A') x P(B)
= (2/7 x 4/5) + (2/5 x 5/7)
= (8/35 + 10/35) = 18/35

Hence, option 4 is the correct answer.