Pursuit problem with start delay A thief steals a car at 1:30 p.m. driving 45 km/h. The theft is discovered at 2:00 p.m., and the owner starts at 50 km/h. At what time will the owner catch the thief?

Difficulty: Medium

Correct Answer: 6:30 p.m.

Explanation:


Introduction / Context:
Classic chase problems compare the initial head start to the relative speed. The pursuer closes the gap at the difference of speeds, provided the pursuer is faster.



Given Data / Assumptions:

  • Thief speed = 45 km/h, starts at 1:30 p.m.
  • Owner speed = 50 km/h, starts at 2:00 p.m.
  • Uniform speeds; straight route.


Concept / Approach:
Head start distance = thief speed * start gap (0.5 h). Catch-up time after the owner starts equals head start / relative speed.



Step-by-Step Solution:

Head start = 45 * 0.5 = 22.5 kmRelative speed = 50 − 45 = 5 km/hCatch-up time = 22.5 / 5 = 4.5 hCatch-up clock time = 2:00 p.m. + 4.5 h = 6:30 p.m.


Verification / Alternative check:
Distances at 6:30 p.m.: thief drives 5 h from 1:30 ⇒ 225 km; owner drives 4.5 h from 2:00 ⇒ 225 km.



Why Other Options Are Wrong:
Earlier times ignore the 22.5 km head start or use the wrong relative speed.



Common Pitfalls:
Adding speeds (for opposite directions) or forgetting the 30-minute start delay.



Final Answer:
6:30 p.m.

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