A car travels a distance A to B at a speed of 40 kmh^-1 and return to A at a speed of 30kmh^-1. what is the average speed for the whole journey
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A car travels a distance A to B at a speed of 40 kmh^-1 and return to A at a speed of 30kmh^-1. what is the average speed for the whole journey.
Answer ->
Let distance between A and B = x km
Time taken to travel from A to B = ( x/40 ) hr
Time taken to travel from B to A = ( x/30 ) hr
total time of journey = (x/40) + (x/30) = (7/120) x hr
total distance travelled = 2x km
average speed = (total distance)/(total time) = 2x / [ (7/120) x ] = ( 240/7 ) km/hr ≈ 34.3 km/hr
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