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.**