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  • Question
  • The probabilities that A and B will tell the truth are 2 / 3 and 4 / 5 respectively . What is the probability that they agree with each other ?


  • Options
  • A. 3/5
  • B. 1/3
  • C. 2/5
  • D. 3/4

  • Correct Answer
  • 3/5 

    Explanation

    Let A be the event of A will tell truth. B be the event of B tell truth

     

      P ( A ) = 2 3 , P ( A c ) = 1 - P ( A ) = 1 3

     

     

     

    P ( B ) = 4 5 , P ( B c ) = 1 - P ( B ) = 1 5  

     

    When both agree then they say true or they say false together, that is 

     

      A ? B   o r   A c ? B c

     

     

     

    Also these events will be mutually exclusive :

     

      P ( A ? B ) + P ( A c ? B c ) = P ( A ) P ( B ) P ( C ) = 2 3 * 4 5 + 1 3 * 1 5 = 3 5


  • More questions

    • 1. The difference between simple and compound interests compounded annually on a certain sum of money for 2 years at 4% per annum is Re. 1. The sum (in Rs.) is:

    • Options
    • A. 625
    • B. 635
    • C. 645
    • D. 655
    • Discuss
    • 2. What is the sum of the first 13 terms of an arithmetic progression if the first term is -10 and last term is 26?

    • Options
    • A. 104
    • B. 140
    • C. 84
    • D. 98
    • Discuss
    • 3. Arrange the following words will come in first if all of them are arranged alphabetically as in a dictionary?

    • Options
    • A. Collotype
    • B. Colon
    • C. College
    • D. Collective
    • Discuss
    • 4. The compound interest on Rs. 30,000 at 7% per annum is Rs. 4347. The period (in years) is:

    • Options
    • A. 2
    • B. 3
    • C. 4
    • D. 5
    • Discuss
    • 5. If the number 583_437 is completely divisible by 9, then the smallest whole number in the place of the blank digit will be

    • Options
    • A. 4
    • B. 5
    • C. 3
    • D. 6
    • Discuss
    • 6. How many pairs of letters are there in the word 'SEQUENTIAL' which have as many letters between them as are in the alphabet ?

    • Options
    • A. Four
    • B. One
    • C. Two
    • D. Three
    • Discuss
    • 7. For S = $21,000, payments (R) of $1500 at the end of each 6-month periodi= 10% compounded semi-annually. Find the minimum number of payments to accumulate 21,000.

    • Options
    • A. 10
    • B. 11
    • C. 12
    • D. 13
    • Discuss
    • 8. The sum of a non-zero number and thrice its reciprocal is 52/7. Find the number.

    • Options
    • A. 8
    • B. 9
    • C. 7
    • D. 6
    • Discuss
    • 9. What is the next letter in the given series M N J Q G ?

    • Options
    • A. U
    • B. S
    • C. T
    • D. H
    • Discuss
    • 10. Among three numbers, the first is twice the second and thrice the third. If the average of three numbers is 429, then what is the difference between the first and the third number?

    • Options
    • A. 412
    • B. 468
    • C. 517
    • D. 427
    • Discuss


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