UPSC Prelims 2010 Q39: Science & Technology – Logical Reasoning & Puzzles
- (a) R
- (b) Q
- (c) P
- (d) M
Answer: (b) Q
Explanation
A seating-arrangement logic puzzle: who faces N?
Six people (M, N, O, P, Q, R) sit in two facing rows of three, with seats directly opposite each other.
| Clue | Deduction |
|---|---|
| Q not at the end of any row | Q sits in a middle seat of one row |
| P is second to the left of R | P and R sit at opposite ends of the same row (e.g., left end and right end) |
| O is Q's neighbour AND diagonally opposite P | Since P and R occupy one row's ends, Q must be in the other row's middle seat; O, Q's neighbour, sits at one end of that row, specifically the one diagonally opposite P |
| N is R's neighbour | Since R is at a row-end, its only same-row neighbour is the middle seat of R's row |
Working through the full arrangement: Row 1 = P, N, R (P and R at the ends, N in the middle); Row 2 = M, Q, O (Q in the middle, O diagonally opposite P, M filling the remaining seat). Since each column faces directly across, N (Row 1, middle) faces Q (Row 2, middle).
Final arrangement (each column faces the one below it):
| Row | Seat 1 | Seat 2 | Seat 3 |
|---|---|---|---|
| Row 1 | P | N | R |
| Row 2 | M | Q | O |
Answer: (b) Q.
Why each option is right or wrong
- (a) Incorrect. R sits at the end of Row 1, facing O, not N.
- (b) CORRECT. Working through the seating logic places Q directly opposite N in the facing row.
- (c) Incorrect. P sits at the other end of Row 1, facing M, not directly relevant to who faces N.
- (d) Incorrect. M faces P, not N, in this arrangement.
Key point
Working through all four clues systematically places N in Row 1's middle seat and Q in Row 2's middle seat, directly facing each other — so Q faces N.
Remember
Seating puzzle: N (Row 1 middle) faces Q (Row 2 middle) after working through all seating clues.
Common mistakes
- Not setting up a clear grid/row structure before applying each clue in sequence.
- Misreading 'second to the left of' as adjacent rather than two positions apart.
- Confusing same-row neighbours with diagonal or facing relationships.
Exam tip
For facing-row seating puzzles, sketch both rows first, place end-position clues (like P-R), then fill middles and diagonals step by step.
Sources
- R. S. Aggarwal — A Modern Approach to Verbal and Non-Verbal Reasoning (Puzzle Test)
- Arun Sharma — How to Prepare for Logical Reasoning for the CAT (arrangement and attribute-matching puzzles)