Data sufficiency — Who is the uncle of L? Statements: A. P, brother of M, is father of L; M is father of S. B. R is father of L's cousin. Decide which statements are sufficient to determine the uncle of L.
Correct Answer: A alone is sufficient
Introduction / Context:The task is to identify L’s uncle using data sufficiency. We must determine whether each statement alone (or together) pins down a unique answer.
Given Data / Assumptions:
- A: P and M are brothers; P is father of L; M is father of S.
- B: R is father of L’s cousin (ambiguous without further ties).
Concept / Approach:An uncle is a brother of a parent (or spouse thereof, depending on convention). From A, we know P is L’s father and that P’s brother is M, i.e., M is paternal uncle of L.
Step-by-Step Solution:
1) From A: Since P (male) and M (male) are brothers, and P is L’s father, M is L’s paternal uncle by definition.2) From B: Knowing only that R is father of L’s cousin does not reveal whose sibling R is, nor fix which side of the family produces the cousin. B is insufficient.Verification / Alternative check:Under A, there is no ambiguity: the uncle is M. Under B, R could be any cousin’s father through various family branches; multiple possibilities exist.
Why Other Options Are Wrong:
- B alone: Too vague to identify a unique uncle.
- Either A or B: False, as B fails.
- Both not sufficient: False, A is already sufficient.
- A and B together: Redundant since A alone suffices.
Common Pitfalls:Mistaking any cousin’s parent as automatically an uncle; overlooking that “cousin” may arise from either parent’s siblings.
Final Answer:A alone is sufficient.