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Home Aptitude Probability Comments

  • Question
  • 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


  • Options
  • A. 30/100
  • B. 35/100
  • C. 45/100
  • D. 50/100

  • Correct Answer
  • 35/100 

    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%


  • Probability problems


    Search Results


    • 1. A bag contains 50 tickets numbered 1,2,3,4......50 of which five are drawn at random and arranged in ascending order of magnitude.Find the probability that third drawn ticket is equal to 30.

    • Options
    • A. 551/15134
    • B. 1/2
    • C. 552/15379
    • D. 1/9
    • Discuss
    • 2. Three unbiased coins are tossed. What is the probability of getting at most two heads?

    • Options
    • A. 3/4
    • B. 7/8
    • C. 1/2
    • D. 1/4
    • Discuss
    • 3. A bag contains 2 red Roses, 4 yellow Roses and 6 pink Roses. Two roses are drawn at random. What is the probability that they are not of same color?

    • Options
    • A. 1/6
    • B. 2/3
    • C. 14/33
    • D. 5/6
    • Discuss
    • 4. In a class, 30% of the students offered English, 20% offered Hindi and 10% offered both. If a student is selected at random, what is the probability that he. has offered English or Hindi ?

    • Options
    • A. 1/2
    • B. 3/4
    • C. 4/5
    • D. 2/5
    • Discuss
    • 5. If two letters are taken at random from the word HOME, what is the probability that none of the letters would be vowels?

    • Options
    • A. 1/6
    • B. 1/2
    • C. 1/3
    • D. 1/4
    • Discuss
    • 6. A bag contains 4 red and 3 black balls. A second bag contains 2 red and 4 black balls. One bag is selected at random. From the selected bag, one ball is drawn. Find the probability that the ball drawn is red.

    • Options
    • A. 23/42
    • B. 19/42
    • C. 7/32
    • D. 16/39
    • Discuss
    • 7. There are 26 balls marked with alphabetical order A to Z. What is the probability of selecting vowels listed balls?

    • Options
    • A. 1
    • B. 21/26
    • C. 5/26
    • D. 5
    • Discuss
    • 8. A word consists of 9 letters; 5 consonants and 4 vowels.Three letters are choosen at random. What is the probability that more than one vowel will be selected ?

    • Options
    • A. 13/42
    • B. 17/42
    • C. 5/42
    • D. 3/14
    • Discuss
    • 9. Three houses are available in a locality. Three persons apply for the houses. Each applies for one house without consulting others. The probability that all the three apply for the same house is :

    • Options
    • A. 2/9
    • B. 1/9
    • C. 8/9
    • D. 7/9
    • Discuss
    • 10. The probabilities that a student will receive an A, B, C or D grade are 0.4, 0.3 , 0.2 and 0.1 respectively. Find the probability that a student will receive Atleast B grade.

    • Options
    • A. 0.21
    • B. 0.3
    • C. 0.7
    • D. None of these
    • Discuss


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