A thief is noticed by a policeman from a distance of 200 m

A thief is noticed by a policeman from a distance of 200 m. The thief starts running and the policeman chases him. The thief and the policeman run at a speed of 10 km/h and 11 km/h respectively. What is the distance between them after 6 minutes.

  1. 100 m
  2. 120 m
  3. 150 m
  4. 160 m

Answer

Speed of the policeman = 11 × (5 / 18) m / s

Speed of the thief = 10 × (5 / 18) m / s

After 6 minutes distance travelled by the policeman = 11 × (5 / 18) × 6 × 60 m

After 6 minutes distance travelled by the thief = 10 × (5 / 18) × 6 × 60 m

But the thief was already 200 m ahead, so distance between the two is given by : 

(10 × (5 / 18) × 6 × 60 m + 200 ) -  11 × (5 / 18) × 6 × 60 m

= (10 × 5 × 20 + 200) - 11 × 5 × 20 m = 1200 - 1100 m = 100 m

The correct option is A.