Question

cover distance 1000 km at 4km/hr and The return journey 3km/hr. what is the average speed??​

Answer 1

Answer:

Average speed = 3.428km/h

Step-by-step explanation:

Distance covered is same in both cases which is 1000km.

We know, Speed = Distance/Time

So, Time = Distance/Speed

In Case I, speed = 4km/h

Time = Distance/Speed

= 1000/4

= 250h

In Case II, speed = 3km/h

Time = Distance/Speed

= 1000/3

= 333.34h

Average speed

= Total Distance/Total Time

= 1000+1000/250+333.34

= 2000/583.34

= 3.428km/h

[Here I used calculator]

Average speed can be directly calculated by the formula,

= 2×V1×V2 / (V1+V2)

(V1 = Speed in first case,

V2 = Speed in second case)

= 2×3×4 / (3+4)

= 24/7

= 3.428km/h

[Note this formula is only applicable if distance in both cases is same and time is not given.]

If time in both cases is same, and distance is not given,

Average speed = (V1 + V2)/2

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