Correct Answer - Option 2 : 22.5 kmph
Given:
Speed for 50 km distance = 25 kmph
Speed for 40 km distance = 20 kmph
Formula Used:
Average Speed = Total Distance/Total Time
Calculations:
Speed for 50 km distance = 25 kmph
Speed for 40 km distance = 20 kmph
Total distance = (50 + 40) km
⇒ Total distance = 90 km
Total Time = (50/25) + (40/20)
⇒ Total Time = (2 + 2) hrs. = 4 hrs.
Average Speed = Total Distance/Total Time
⇒ Average Speed = 90/4 = 22.5kmph
∴ The average speed for the whole journey is 22.5 kmph.