Data Sufficiency — Taller Girls Than Shravan Question: How many girls are taller than Shravan in his class? Statements: I. Ranking all students in descending height, Shravan is 17th from the top overall and 12th among boys. II. Shravan's rank from the bottom is 18th among boys and 29th among all students.

Difficulty: Medium

Correct Answer: I alone is sufficient while II alone is not sufficient

Explanation:


Introduction / Context:
Determine the number of girls taller than Shravan using ranking information. Treat the class as a single ordered list while also using the boys-only ordering. Data Sufficiency asks whether the statements give enough information independently.


Given Data / Assumptions:

  • From Statement I: Shravan is 17th overall from the top; 12th among boys from the top.
  • From Statement II: Shravan is 18th among boys from the bottom; 29th among all from the bottom.
  • Total class size is not explicitly provided; it may or may not be needed.


Concept / Approach:
Number of people taller than Shravan overall is (overall top rank - 1). Number of boys taller than Shravan is (boys top rank - 1). Girls taller than Shravan = (overall taller) - (boys taller).


Step-by-Step Solution:

Using I: Overall taller than Shravan = 17 - 1 = 16. Boys taller than Shravan = 12 - 1 = 11. Girls taller than Shravan = 16 - 11 = 5. So Statement I alone is sufficient. Using II: From bottom ranks, we need totals to convert to top ranks: overall top rank = N - 29 + 1; boys top rank = B - 18 + 1. Without knowing N (total students) and B (total boys), we cannot compute a definite count of taller girls. Hence II alone is not sufficient.


Verification / Alternative check:
The result 5 depends only on relative positions from Statement I and does not require total class or total boys counts.


Why Other Options Are Wrong:

  • II alone sufficient: False—totals unknown.
  • Either alone sufficient: False—only I works.
  • Neither sufficient: False—I suffices.
  • Both required: Unnecessary; I alone is enough.


Common Pitfalls:
Forgetting to subtract 1 when converting a rank to the count of people ahead; assuming totals that are not given; mixing up top and bottom rankings.


Final Answer:
I alone is sufficient while II alone is not sufficient.

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