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NDA 1 2024 Maths, question 101

Topic: Probability

Q101

A bag contains 55 black and 44 white balls. A man selects two balls at random. What is the probability that both of these are of the same colour ?

  1. (a) 16\frac{1}{6}
  2. (b) 5108\frac{5}{108}
  3. (c) 49\frac{4}{9}Correct answer
  4. (d) 518\frac{5}{18}

Solution.

Answer: (c) 49\frac{4}{9}

  1. The equally likely selections number C(9, 2) = 36.
  2. Same-colour pairs number C(5, 2) + C(4, 2) = 10 + 6 = 16.
  3. The probability is 16/36 = 4/9.