Question

Lorri took a 240 km trip to Waterloo. On her way there, her average speed was 120 km/h. She was stopped for speeding, so on her way home her average speed was 80 km/h. What was her average speed, in km/h, for the entire round-trip?

Answer 1

Average speed is
`96 km/h`

Explanation:

Given: Total distance covered by Lorri is 240 km. For some distance his speed was 120 km/h and for the rest of the distance, speed is 80 km/h

To find: Average speed for the entire trip

Solution:

On her way to Waterloo:

Distance covered = 240 km

Speed = 120 km/h

Time = Distance /speed =
`(240)/(120) =2\,\,hours`

On her way to home:

Distance covered = 240 km

Speed = 80 km/h

Time = Distance /speed =
`(240)/(80)=3\,\,hours`

Total distance covered by Lurri = 240 + 240 = 480 km

Total time =
`2+3=5\,\,hours`

Average speed = Total distance/Total time taken =
`(480)/(5)=96\,\,km/h`