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Q: A box contains 5 green, 4 yellow and 5 white pearls. Four pearls are drawn at random. What is the probability that they are not of the same colour ?

  • 1
    11/91
  • 2
    4/11
  • 3
    1/11
  • 4
    90/91
  • Show Answer
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Answer : 4. "90/91"
Explanation :

Answer: D) Option D Explanation: Let S be the sample space. Then,n(s) = number of ways of drawing 4 pearls out of 14 = C414 ways = 14×13×12×114×3×2×1= 1001 Let E be the event of drawing 4 pearls of the same colour.Then, E = event of drawing (4 pearls out of 5) or (4 pearls out of 4) or (4 pearls out of 5)   ⇒C15+ C44+ C15 = 5+1+5 =11  P(E) = n(E)n(S)=111001=191      Required probability = 1-191=9091

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