Question

A train covers its journey from A to B with a speed of 40 km/h and while returning
along the same line the speed is 30 km/h, find the average speed for the entire
journey.​

Answer 1

Answer:

35km is the average speed

Step-by-step explanation:

avg = total / 2

=40+30/2

=35

Answer 2

Answer: 20km/h

Step-by-step explanation:

Average speed = total distance / total time

Let the distance between A and B be x.

Total distance = 2x

s₁ = d / t₁

40 km/h = x / t₁

⇒ t₁ = x/40

s₂ = d / t₂

30 = x / t₂

⇒ t₂ = x/30

Total time = t₁ + t₂

                 = x/40 + x/30

                 = (3x + 4x)/120

                = 7x/120  

Total time = 7x/120

⇒ Average speed = 2x/7x/120 = (2x × 120)/7x = 140x/7x = 20km/h

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