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NDA 2 2024 Maths, question 116

Topic: Probability

Q116

Two perfect dice are thrown. What is the probability that the sum of the numbers on the faces is neither 99 nor 1010?

  1. (a) 1/361/36
  2. (b) 5/365/36
  3. (c) 7/367/36
  4. (d) 29/3629/36Correct answer

Solution.

Answer: (d) 29/3629/36

  1. Among 36 ordered dice outcomes, sum 9 occurs in four ways and sum 10 in three ways.
  2. These events are disjoint.
  3. The complement has probability 1−7/36=29/36.