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.**