A car travels from place a to b at 20 km/hour and returns at 30 km/hour.The average speed of the car for whole journey is
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let's the distance between a and b be x
avg speed = total distance/total time
time in going from a to b
time = distance/speed
t1= x/20 hour
time while returning from b to a
t2 = x/30 hour
avg speed = x/(x/20)+x/(x/30)
=x+x/(30x+20x/600)
=2x/(50x/600)
=2x/(x/12)
=24 km/hour
avg speed = total distance/total time
time in going from a to b
time = distance/speed
t1= x/20 hour
time while returning from b to a
t2 = x/30 hour
avg speed = x/(x/20)+x/(x/30)
=x+x/(30x+20x/600)
=2x/(50x/600)
=2x/(x/12)
=24 km/hour
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