If 4 marbles are drawn at random, what is the probability that 2 are red and 2 are blue ?

  • 11/16
  • 3/16
  • 11/72
  • 3/65
  • None of these
  • Explanation:

    Total number of marbles = 8+3+5 = 16

    n(S) = Exhaustive number of cases

    Number of ways of drawing 4 marbles out of 16 = 16C4

    = 16×15×14×13/1×2×3×4 = 1820

    n(E) = Number of cases when 2 marbles are red and 2 are blue

    8C2 × 3C2 = 8×7/1×2 × 3×2/1×2 = 84

    ∴ Required probability = 84/1820 = 3/65

If 4 marbles are drawn at random, what is the probability that 2 are red and 2 are blue ?
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