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

  • 1
    (1/2)^11
  • 2
    (9)(1/2)
  • 3
    (11C2)(1/2)^9
  • 4
    (1/2)
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Answer : 1. "(1/2)^11"
Explanation :

Answer: A) (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 =122×129=1211

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