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  • Question
  • A fair coin is tossed 11 times. What is the probability that only the first two tosses will yield heads ?


  • Options
  • A. (1/2)^11
  • B. (9)(1/2)
  • C. (11C2)(1/2)^9
  • D. (1/2)

  • Correct Answer
  • (1/2)^11 

    Explanation

    Probability of occurrence of an event, 

    P(E) = Number of favorable outcomes/Numeber of possible outcomes = n(E)/n(S)


    ? Probability of getting head in one coin = ½, 

    ? Probability of not getting head in one coin = 1- ½ = ½, 

    Hence, 

    All the 11 tosses are independent of each other.

    ? Required probability of getting only 2 times heads = 1 2 2 × 1 2 9 = 1 2 11


  • Probability problems


    Search Results


    • 1. A number is selected at random from the numbers 1 to 30. What is the probability that it is divisible by either 3 or 7 ?

    • Options
    • A. 1/30
    • B. 2/30
    • C. 1/25
    • D. 1/2
    • Discuss
    • 2. A box contains 100 balls, numbered from 1 to 100. If three balls are selected at random and with replacement from the box, what is the probability that the sum of the three numbers on the balls selected from the box will be odd?

    • Options
    • A. 1/6
    • B. 1/3
    • C. 1/2
    • D. 1/4
    • Discuss
    • 3. In a throw of a coin, find the probability of getting a head.

    • Options
    • A. 1
    • B. 1/2
    • C. 1/4
    • D. 0.1
    • Discuss
    • 4. The letters of the word CASTIGATION is arranged in different ways randomly. What is the chance that vowels occupy the even places ?

    • Options
    • A. 0.04
    • B. 0.043
    • C. 0.047
    • D. 0.05
    • Discuss
    • 5. The day before yesterday, I was 25 years old, and next year I will turn 28. How is it possible?

    • Options
    • A. 31 Dec
    • B. 30 Dec
    • C. 1 Jan
    • D. 28 Feb
    • Discuss
    • 6. 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
    • 7. A dice is numbered from 1 to 6 in different ways. If 1 is adjacent to 2, 4 and 6, then which of the following statements is necessarily true?

    • Options
    • A. 2 is opposite to 6
    • B. 1 is adjacent to 3
    • C. 3 is adjacent to 5
    • D. 3 is opposite to 5
    • Discuss
    • 8. Four usual dice are thrown on the ground. The total of numbers on the top faces of these four dice is 13 as the top faces showed 4, 3, 1 and 5 respectively. What is the total of the faces touching the ground?

    • Options
    • A. 12
    • B. 13
    • C. 15
    • D. Cannot be determined
    • Discuss
    • 9. A dice is numbered from 1 to 6 in different ways. If 1 is adjacent to 2, 3 and 5, then which of the following statements is necessarily true?

    • Options
    • A. 4 is adjacent to 6
    • B. 2 is adjacent to 5
    • C. 1 is adjacent to 6
    • D. 1 is adjacent to 4
    • Discuss
    • 10. A cube is painted blue on two adjacent surfaces and black on the surfaces opposite to blue surfaces and green on the remaining faces .Now the cube is cut into 216 smaller cubes of equal size.

    • Options
    • A. 56
    • B. 48
    • C. 32
    • D. 64
    • Discuss


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