Correct Answer - Option 3 : 84 km/h
GIVEN:
Distance = 280 km
Total time = 3.5 hours
Speed in one-fourth journey = 70 km/h
FORMULA USED:
Speed = Distance/Time
CALCULATION:
One-fourth distance = 280/4 = 70 km
Time taken to cover one-fourth distance = 70/70 = 1 hour
Remaining distance = 280 - 70 = 210 km
Remaining Time = 3.5 - 1 = 2.5 hours
Required speed = 210/2.5 = 84 km/h
∴ Speed for the remaining journey should be 84 km/h.