Question

Saurabh starts walking at a speed of 60 km / h 4 hours before Gurgaon, then Sahil follows him at a speed of 80 km / h. What will be the difference in time when Saurabh will be 40 km ahead of Sahil and Sahil will be 50 km ahead of Saurabh?​

Answer 1

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$\bold{Explanation:}$

Distance between Gurgaon and Delhi = S km

Time taken to go from Delhi to Gurgaon = S / 60 hours

Time taken to return = S / 40 hours

Total time = S [ 1/40 + 1/60 ] = S/24 hours

Average speed for the entire journey = total distance / total time duration 

                     =  2 S / ( S/24)  = 48 kmph