Three dice rolled: at least one shows 2: Three fair six-faced dice are rolled. How many outcomes in the 6^3 sample space have at least one die showing 2?

Difficulty: Easy

Correct Answer: 91

Explanation:


Introduction / Context:
Counting “at least one” events on dice is best done via the complement rule: subtract the count with no 2s from the total sample space of 6^3 equiprobable outcomes.


Given Data / Assumptions:

  • Three independent fair dice, faces {1,…,6}.
  • We count ordered triples (d1, d2, d3).


Concept / Approach:

  • Total outcomes = 6^3.
  • No-2 outcomes: each die has 5 allowed faces (exclude 2) → 5^3.
  • At least one 2 = 6^3 − 5^3.


Step-by-Step Solution:

Total = 6^3 = 216No-2 = 5^3 = 125Count = 216 − 125 = 91


Verification / Alternative check:
Inclusion–exclusion by exact number of 2s (1, 2, 3) yields the same 91; complement is simpler.


Why Other Options Are Wrong:

  • 36 and 81 are too small; 116 exceeds total remaining after subtraction.


Common Pitfalls:

  • Mixing “count of outcomes” with “probability.”


Final Answer:
91

More Questions from Permutation and Combination

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion