A bus driver must complete a 240 km trip in 4 hours. If he averages 70 km an hour for the first 3 hours of his trip. how fast must he travel (in km/h) in the last/final hour?  

Given:

A bus driver must complete a 240 km trip in 4 hours. He averages 70 km/h for the first 3 hours of his trip.

Concept:

To find the required speed for the last hour, we need to determine the remaining distance and then calculate the speed needed to cover that distance in the remaining time.

Calculation:

Total distance to be covered = 240 km

Total time available = 4 hours

Distance covered in the first 3 hours:

⇒ Distance = Speed × Time

⇒ Distance = 70 km/h × 3 hours

⇒ Distance = 210 km

Remaining distance to be covered in the final hour:

⇒ Remaining distance = Total distance - Distance covered in the first 3 hours

⇒ Remaining distance = 240 km - 210 km

⇒ Remaining distance = 30 km

Speed required to cover the remaining distance in the final hour:

⇒ Speed = Distance / Time

⇒ Speed = 30 km / 1 hour

⇒ Speed = 30 km/h

∴ The bus driver must travel at 30 km/h in the last hour.