Three fair coins tossed together: What is the probability that all three coins show the same face (either all heads or all tails)?

Difficulty: Easy

Correct Answer: 1/4

Explanation:

Introduction / Context:Tossing three fair coins creates 2^3 equally likely outcomes. We want the probability of the event where all faces match, i.e., either HHH or TTT.

Given Data / Assumptions:

  • Coins are fair and independent.
  • Sample space size = 8 outcomes.

Concept / Approach:Count favorable outcomes and divide by total outcomes. Favorable = {HHH, TTT} = 2 outcomes.

Step-by-Step Solution:

Total outcomes = 8Favorable outcomes = 2P(all same) = 2/8 = 1/4

Verification / Alternative check:Compute P(HHH) + P(TTT) = (1/2)^3 + (1/2)^3 = 1/8 + 1/8 = 1/4.

Why Other Options Are Wrong:1/3 results from averaging; 1/6 confuses with “exactly two heads”; 1/8 counts only one of the two symmetric cases.

Common Pitfalls:Forgetting to include both all-heads and all-tails; mixing up “all same” with “all heads.”

Final Answer:1/4

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