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  • Question
  • A brother and a sister appear for an interview against two vacant posts in an office. The probability of the brother?s selection is 1/5 and that of the sister?s selection is 1/3. What is the probability that only one of them is selected?


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

  • Correct Answer
  • 2/5 

    Explanation

    Probability that only one of them is selected = (prob. that brother is selected) × (prob. that sister is not selected) +  (Prob. that brother is not selected) × (Prob. that sister is selected)

     

    1 5 * 2 3 + 4 5 * 1 3 2 5


  • Probability problems


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    • 1. Out of first 20 natural numbers, one number is selected at random. The probability that it is either an even number or a prime number is ?

    • Options
    • A. 16/19
    • B. 1
    • C. 3/2
    • D. 17/20
    • Discuss
    • 2. A card is drawn from a pack of 52 cards. The probability of getting a queen of the club or a king of the heart is?

    • Options
    • A. 1/26
    • B. 1/13
    • C. 2/13
    • D. 1/52
    • Discuss
    • 3. In a simultaneous throw of two dice, what is the probability of getting a total of 7 ?

    • Options
    • A. 1/6
    • B. 1/4
    • C. 1/20
    • D. 3/4
    • Discuss
    • 4. Out of sixty students, there are 14 who are taking Economics and 29 who are taking Calculus. What is the probability that a randomly chosen student from this group is taking only the Calculus class ?

    • Options
    • A. 8/15
    • B. 7/15
    • C. 1/15
    • D. 4/15
    • Discuss
    • 5. In a box, there are four marbles of white color and five marbles of black color. Two marbles are chosen randomly. What is the probability that both are of the same color?

    • Options
    • A. 2/9
    • B. 5/9
    • C. 4/9
    • D. 0
    • Discuss
    • 6. A bag contains 7 green and 5 black balls. Three balls are drawn one after the other. The probability of all three balls being green, if the balls drawn are not replaced will be:

    • Options
    • A. 123/897
    • B. 23/67
    • C. 7/44
    • D. 12/45
    • Discuss
    • 7. One card is drawn from a pack of 52 cards, each of the 52 cards being equally likely to be drawn find the probability the card drawn is red.

    • Options
    • A. 2/3
    • B. 1/2
    • C. 1/52
    • D. 13/51
    • Discuss
    • 8. A bag contains 8 red and 4 green balls. Find the probability that two balls are red and one ball is green when three balls are drawn at random.

    • Options
    • A. 56/99
    • B. 112/495
    • C. 78/495
    • D. None of these
    • Discuss
    • 9. If P(A)=4/9;then the odd against the event A is:

    • Options
    • A. 4:9
    • B. 4:5
    • C. 5:4
    • D. 4:14
    • Discuss
    • 10. If a card is drawn at random from a pack of 52 cards,what is the chance of getting a spade or ace?

    • Options
    • A. 0.25
    • B. 5/13
    • C. 0.20
    • D. 4/13
    • Discuss


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