Lesson eLearning

A fair die is rolled twice. What is the probability that at least one of the two rolls shows a 4?

medium 2 marks Class 9 · Mathematics · Statistics
Answer
11/36

The correct answer is 11/36 — Hence the required probability is .

Step-by-step solution

  1. Identify the complementary event: neither roll shows a 4.
  2. The probability that a single roll is not a 4 is because there are 5 other faces.
  3. Since the two rolls are independent, the probability that neither roll shows a 4 is .
  4. The probability of the desired event is the complement: .
  5. Hence the required probability is .
Common mistake: Adding probabilities of two rolls incorrectly instead of using complement

Concept tested: Complementary event probability with independent trials

Published · How this solution was prepared and checked

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