Correct Answer - Option 4 : (28 + 1/3) km/h
GIVEN:
Total distance = 680 km
Total time = 8 hours
Time taken to cover half distance = 8/5 × total time
FORMULA USED:
Speed = Distance/Time
CALCULATION:
Average speed of journey = 680/8 = 85 km/h
Time taken to cover half distance = 5/8 ×8 = 5 hours
Remaining time = 8 - 5 = 3 hours
Remaining distance = 680/2 = 340 kms
Speed for remaining journey = 340/3 = (113 + 1/3)km/h
Required difference = (113 + 1/3) - 85 = (28 + 1/3) km/h
∴ The answer is (28 + 1/3) km/h.