A thief is noticed by a policeman from a distance of 800m. The thief starts running and the policeman chases him. The thief and the policeman run at speeds of 20km/h and 25km/h, respectively. What is the distance between them after 9 minutes?
- A50 metres
- B100 metres
- C70 metres
- D90 metres
Solution & Step-by-step Explanation
Given:
Initial distance = 800m
Speed of thief = 20km/h
Speed of policeman = 25km/h
Since they run in the same direction, the relative speed is:
Relative Speed=25−20=5km/h
Convert the relative speed into metres per minute:
5km/h=
60min
5×1000m
=
6
500
m/min=
3
250
m/min
Distance covered by the policeman relative to the thief in 9 minutes:
Distance covered=Relative Speed×Time=
3
250
×9=250×3=750metres
The remaining distance between them after 9 minutes is:
Remaining Distance=Initial Distance−Distance covered=800−750=50metres
Initial distance = 800m
Speed of thief = 20km/h
Speed of policeman = 25km/h
Since they run in the same direction, the relative speed is:
Relative Speed=25−20=5km/h
Convert the relative speed into metres per minute:
5km/h=
60min
5×1000m
=
6
500
m/min=
3
250
m/min
Distance covered by the policeman relative to the thief in 9 minutes:
Distance covered=Relative Speed×Time=
3
250
×9=250×3=750metres
The remaining distance between them after 9 minutes is:
Remaining Distance=Initial Distance−Distance covered=800−750=50metres