Answer : 4 10 km Explanation : Answer: D) 10 km Explanation: Let distance = x km.Time taken at 3 kmph : dist/speed = x/3 = 20 min late.time taken at 4 kmph : x/4 = 30 min earlierdifference between time taken : 30-(-20) = 50 mins = 50/60 hours.x/3- x/4 = 50/60x/12 = 5/6x = 10 km.

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