Arithmetic Ability
 Probability

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Q.

A speaks truth in 75% of cases and B in 80% of cases. In what percentage of cases are they likely to contradict each other, narrating the same incident

View Answer

Correct choice: B

Explanation:

Let A = Event that A speaks the truth B = Event that B speaks the truth Then P(A) = 75/100 = 3/4 P(B) = 80/100 = 4/5 P(A-lie) = 1−3/4 = 1/4 P(B-lie) = 1−4/5 = 1/5 Now, A and B contradict each other =[A lies and B true] or [B true and B lies] = P(A).P(B-lie) + P(A-lie).P(B) = (3/5*1/5)+(1/4*4/5)=7/20 = (7/20*100) = 35%
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