Question

take the horse to overtake the
17. A car completes a journey at an average speed of 40 km/h. At what
speed must it travel on the return journey if the average speed for the
complete journey (out and back) is 60 km/h?
Help

Answer 1

Answer:

• 120 km/h

Step-by-step explanation:

• Speed in one direction = 40 km/h
• Speed on return = x
• Average speed = 60 km/h

Let the distance be d

Average speed

• 2d/(d/40 + d/x) = 60
• d/40 + d/x = 2d/60
• 1/40 + 1/x = 1/30
• 1/x = 1/30 - 1/40
• 1/x = (4-3)/120
• 1/x = 1/120
• x = 120 km/h