P, Q, R and S are four places. To travel from P to R, one travels via Q; to travel from P to S, one travels via both Q and R. Between P and Q there are 3 routes; between Q and R there are 4 routes; and between R and S there are 5 routes. The time taken through these routes… | UPSC CAPF 2026 Q No 70

Accepted Answer: (B) 11

Topic Covered: Quantitative Aptitude and Reasoning

Key Concept: Mathematical relationships, counting and logical analysis

Enumerate combinations of one route from each required leg and add their travel times. Count only the combinations whose total is exactly 7 hours.

The key is to apply the central fact, formula, definition or relationship tested in the question and then eliminate alternatives that do not satisfy it.