Difficulty: Easy
Correct Answer: 7/18
Explanation:
Introduction / Context:
We count ordered pairs (a,b) with a,b ∈ {1,…,6} such that |a − b| ∈ {2,3}. Counting favorable outcomes directly is efficient for small dice problems.
Given Data / Assumptions:
Concept / Approach:
Enumerate the pairs for |a − b| = 2 and for |a − b| = 3. Sum them, divide by 36.
Step-by-Step Solution:
Verification / Alternative check:
Symmetry around the main diagonal implies for each a there are at most two b values satisfying |a − b| = k; tabulation matches the counts above.
Why Other Options Are Wrong:
5/18 corresponds to only one of the difference values; 1/2 greatly overestimates the event; 3/11 is not tied to a 36-sized space.
Common Pitfalls:
Forgetting that outcomes are ordered, or double-counting/omitting symmetric pairs.
Final Answer:
7/18
Discussion & Comments