Question

A bus travels a distance of 120 km with a speed of 40 km/h and returns with a speed of 30 km/h. Calculate the average speed for the entire journey.

Answer 1

distance = 120 km

speed = 30 km/ hr

time = 4 hr

average speed = total distance / total time taken

= 120+120/3+4

=34.2 km / hr

Answer 2

In first case:-

$<b>Speed= 40 km/h$

Distance = 120 km

Therefore, time (t1):

$= \frac{distance}{speed}$

$= \frac{120}{40}$

$= 3 \: hours$

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In second case:-

Speed= 30 km/h

Distance = 120 km

Therefore, time (t2):

$= \frac{120 }{30}$

$= 4 \: hour$

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Now, Average speed -

$= \frac{total \: distance \: covered}{total \: time \: taken}$

$= \frac{120 + 120}{t1 \: + t2}$

$= \frac{240}{3 + 4}$

$= \frac{240}{7}$

$= 34.28 \: km \: per \: hour$

HENCE , AVERAGE SPEED FOR THE ENTIRE JOURNEY IS 34.28 km/hour.