Dear aspirant,
Given :
speed : A to B : V1
speed : B to A : V2
distance : d ( same in both cases)
Than,
time t1 = d/V1
time t2 = d/V2
And total distance : D = d + d = 2d
total time : t = t1 + t2 = d(V1+V2)/(V1V2)
Therefore,
avg speed = D/t = 2(V1V2)/(V1+V2)
Question : A man goes from place A to B at a speed of 12 km/hr and returns from B to A at a speed of 18 km/hr. His average speed for the entire journey is:
Option 1: $14 \frac{2}{5} \mathrm{~km} / \mathrm{hr}$
Option 2: 15 km/hr
Option 3: 6 km/hr
Option 4: 30 km/hr
Question : A man goes from A to B at a speed of 200 km/hr and comes back to A at a speed of 300 km/hr. Find his average speed for the entire journey.
Option 1: 264 km/hr
Option 2: 345 km/hr
Option 3: 340 km/hr
Option 4: 240 km/hr
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