A person goes from point L to N and comes back. His average speed for the whole journey is 100 km/hr. If his speed while coming back from N to L is 65 km/hr, then what will be the speed of the person (in km/hr) while going from L to N?

Speed of the person from point N to L = 65 km/hr

Let speed of the first journey = $$s$$ km/hr

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

=> $$\frac{2\times s\times 65}{s+65}=100$$

=> $$\frac{130s}{s+65}=100$$

=> $$\frac{13s}{s+65}=10$$

=> $$13s=10s+650$$

=> $$13s-10s=3s=650$$

=> $$s=\frac{650}{3}=216.67$$

$$\therefore$$ Speed of the person (in km/hr) while going from L to N = 216.67 km/hr

=> Ans - (D)