Difficulty: Medium
Correct Answer: PR
Explanation:
Introduction / Context:
This classic single-row ordering asks which members must occupy the two ends given a set of left/right inequalities.
Given Data / Assumptions:
Concept / Approach:
Chain the inequalities to build a single consistent order. If A < B and B < C, then A precedes C; the “right of”/“left of” constraints translate directly into < relations.
Step-by-Step Solution:
From P < X < Q and Q < Y < Z we infer P < X < Q < Y < Z.With Z < R, we extend to P < X < Q < Y < Z < R.Thus the only feasible linearization places P at the extreme left and R at the extreme right.
Verification / Alternative check:
Any attempt to push another element to either end violates at least one inequality (e.g., moving X left of P or Y right of R contradicts the chain).
Why Other Options Are Wrong:
Pairs like QZ, XZ, QY include interior elements (Q, X, Y, Z) that cannot sit at ends without breaking inequalities.
Common Pitfalls:
Confusing “to the right of” with “immediately to the right of.” The clues are relative, not necessarily adjacent, except where stated.
Final Answer:
PR
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