Question

A man travels from Delhi to Agra at an average speed of 30km per hour and back at an ave rage speedof 60 km per hour. What’s the average Speed.(a) 48 Km/ hr(b) 40 km/hr(c) 45 km/hr(d) 35 km/hr

Answer 1

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Answer 2

Answer:

(b) 40 km/hr

Explanation:

1- From Delhi to Agra:

The average speed 30 km/hr

Now, the equation relating speed, time and distance is:

Distance = speed * time

Time = distance/speed

Time = distance/30

2- From Agra to Delhi:

The average speed is 60 km/hr

Now, using the same equation as above:

Time = distance/60

To get the total average speed:

Average speed = total distance / total time

Total distance = d + d = 2d

Total time = (d/30) + (d/60)

Average speed = 2d / [(d/30) + (d/60)]

Average speed = 40 km/hr

Hope this helps :)