Data Sufficiency – Ranks from top and bottom (class strength inference) Question: Gaurav ranks 18th from the top in his class. What is his rank from the last? Statements: I. There are 47 students in the class. II. Jatin, who ranks 10th from the top in the same class, ranks 38th from the last.

Introduction / Context:
This DS item tests rank conversion using total class size. If you know the class strength N and a student's rank from the top r, the rank from the bottom is N − r + 1. We assess whether each statement alone gives N.

Given Data / Assumptions:

• Known from the question: Gaurav is 18th from the top.
• I: Class size N = 47.
• II: Jatin is 10th from the top and 38th from the bottom.

Concept / Approach:
The conversion formula is rank_from_bottom = N − rank_from_top + 1. So we only need to know N. Either a direct statement of N or an inference that yields N is sufficient.

Step-by-Step Solution:

Verification / Alternative check:
Both methods yield the same class size (47) and hence the same answer (30 from the last), confirming each statement's sufficiency independently.

Why Other Options Are Wrong:

• I alone or II alone only: both are sufficient, not just one.
• Neither: false because each alone suffices.
• Both: stronger than necessary in DS.

Common Pitfalls:
Omitting the +1 in the conversion formula; mixing up top vs bottom ranks; assuming tie ranks (not stated).

Final Answer:
Either I or II is sufficient