Rashi travelled a distance of 400 km at an average speed of 50 km/h. She covers the first half distance in the first lag in 2 hours, while she covers another lag at half the speed of that of the first lag in 1 hour. What is the speed (in km/h) of the remaining distance?
- A45
- B50
- C60
- D30
Solution & Step-by-step Explanation
Total distance =400 km
Average speed =50 km/h
Total time taken=
Average Speed
Total Distance
=
50
400
=8 hours
Let's look at the first lag:
Distance covered =first half distance=
2
400
=200 km
Time taken =2 hours
Speed in the first lag =
2
200
=100 km/h
Second lag:
Speed =half of the first lag speed=
2
100
=50 km/h
Time taken =1 hour
Distance covered =50×1=50 km
Remaining journey details:
Remaining distance =400−(200+50)=150 km
Remaining time =8−(2+1)=5 hours
Speed for the remaining distance:
Speed=
Remaining Time
Remaining Distance
=
5
150
=30 km/h
Average speed =50 km/h
Total time taken=
Average Speed
Total Distance
=
50
400
=8 hours
Let's look at the first lag:
Distance covered =first half distance=
2
400
=200 km
Time taken =2 hours
Speed in the first lag =
2
200
=100 km/h
Second lag:
Speed =half of the first lag speed=
2
100
=50 km/h
Time taken =1 hour
Distance covered =50×1=50 km
Remaining journey details:
Remaining distance =400−(200+50)=150 km
Remaining time =8−(2+1)=5 hours
Speed for the remaining distance:
Speed=
Remaining Time
Remaining Distance
=
5
150
=30 km/h