Question 384400
a man divide his journey in his three equals part and travells in each of the part with speed of 6o km /hour , 30 km/hour and 10 km/hour .what is the avg speed for total travells?
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total distance = 3d, each section = d
d = rt
t = d/r
t = d/60 + d/30 + d/10 = (18/120)*d = total time for 3d
r = (120/18)*3
r =~ 20 km/hr