Multiple choice

John speaks truth in 70% and Janet in 80% cases. What is the probability that they contradict each other while they are talking about the same incident?

  1. 7/250

  2. 37/100

  3. 27/125

  4. 3/10

  5. 19/50

Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let R: John speaks the truth; and A: Janet speaks the truth. Hence, P(R) = 70/100 and P (R ̅) = 1 - 70/100 = 30/100. Again, P (A) = 80 /100 and P (A ̅) = 1 - 80/100 = 20/100. Therefore, required probability,P(R) × P (A ̅) + P (A) × P (R ̅) = 70/100 x 20/100 + 80/100 x 30/100 = 19/ 50