Question 70

A goes from Point X to Point Y at a speed of 60 km/hr and comes back with a speed of 80 km/hr. What is the average speed (in km/hr) of A for going and coming back?

Solution

Speed of A from point X to Y = 60 km/hr

Speed on return journey = 80 km/hr

Since, equal distances are covered, average speed = harmonic mean of both speeds = $$\frac{2xy}{x+y}$$

= $$\frac{2\times60\times80}{(60+80)}$$

= $$\frac{120\times80}{140}$$

= $$\frac{480}{7}=68.57$$ km/hr

=> Ans - (B)

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