If the probability of A to fail in an examination is 0.2 and that for B is 0.3 , then the probability that either A or B fails (meaning exactly one of - Mathematics MCQ Mathematics Mock Test - 11 2026 | ExamTest.live

mediumMCQMathematics Mock Test - 112026Mathematics

1 mark

If the probability of A to fail in an examination is 0.2 and that for B is 0.3, then the probability that either A or B fails (meaning exactly one of them fails) is:

Solution & Step-by-step Explanation

Let F_{A} be the event that A fails and F_{B} be the event that B fails. P (F_{A}) = 0.2 ⟹ P (F_{A}^{'}) = 0.8 (A passes) P (F_{B}) = 0.3 ⟹ P (F_{B}^{'}) = 0.7 (B passes)The probability that exactly one fails: = P (A fails and B passes) + P (A passes and B fails) = P (F_{A}) P (F_{B}^{'}) + P (F_{A}^{'}) P (F_{B}) = (0.2) (0.7) + (0.8) (0.3) = 0.14 + 0.24 = 0.38 .

Try it yourself before checking the explanation above.

If the probability of A to fail in an examination is 0.2 and that for B is 0.3, then the probability that either A or B fails (meaning exactly one of them fails) is:

0.5

0.38

0.8

0.25

Practice with timed mock tests and track your performance across Mathematics.