A policeman spots a thief 200 m ahead. The thief runs at 10 km/h and the policeman chases at 11 km/h. After 6 minutes of running, what is the distance between them (in metres)?

Introduction / Context:
Pursuit problems use relative speed along a straight line. The gap closes at (chaser speed − runner speed). Once we find how much is closed in the given time, we subtract from the initial lead to get the remaining separation.

Given Data / Assumptions:

• Initial lead L = 200 m.
• Speeds: thief = 10 km/h, policeman = 11 km/h.
• Time t = 6 minutes = 360 s.

Concept / Approach:
Relative speed = (11 − 10) km/h = 1 km/h. Convert 1 km/h to m/s: 1000/3600 ≈ 0.277777… m/s. Distance closed in time t equals relative_speed * t.

Step-by-Step Solution:

Verification / Alternative check:
In 6 minutes, thief covers (10 km/h)*(0.1 h)=1 km; policeman covers (11 km/h)*(0.1 h)=1.1 km; difference 0.1 km = 100 m—same result.

Why Other Options Are Wrong:
180/150/125 m do not match the closed distance computed from the correct relative speed.

Common Pitfalls:
Adding speeds when both move in the same direction; mixing metres and kilometres without proper conversion.

Final Answer:
100 m