Can u solve this Math question?

"A" speaks truth in 75% cases n "B" in 80% cases.In what % of cases are they likely to contradict each other,narrating the same incident? a)5% b)15% c)35% d)45% The ans is 35% can anyone explain how n why??

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  • Anonymous
    9 years ago
    Favorite Answer

    The way I read it, you want the probability of them contradicting each other. This can occurs in two ways, either

    A.)Person A tells the truth (75% chance) and B lies (20% chance)

    OR

    B.)Person A lies (25% chance) and person B tells the truth (80% chance)

    To find the total chance, you find the chance of either of those events occurring then add them together. So,

    Chance of event A occurring=.75*.20=.15

    Chance of event B occurring=.25*.8=.2

    So added together, Chance A+Chance B=.35 or 35%. Does that make sense?

  • 9 years ago

    If A speaks the truth, there is a 15% chance B will be contradicting because 3/4 * 1/5 = 3/20 = 15%

    If B speaks the truth, there is a 20% chance A will be contradicting because 4/5 * 1/4 = 4/20 = 20%

    15 + 20 = 35%

  • 9 years ago

    Here is what i think:

    for them to contradict each other either A says a truth and B lies or A lies and B says a truth.

    For the first case (A truth, B lie) , the probability is:

    .75*(1-.8)=.75*.2=.15

    For the second case (A lie, B truth):

    (1-.75)*.8=.25*.8=.2

    So there is a 15% chance of case 1 and a 20% chance of case 2. But you want to know the total:

    15%+20%=35%

    This is what I would think just using logic.

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