Speed of boat in still water is 5 km/hr and speed of current is 1 km/hr. The boat takes total 75 min to go to some point and come back at the starting point. Find the distance between two points.
Answer & explanation
Correct answer: option 2
Speed of boat in downstream = 5 + 1 = 6 km/hr
Speed of boat in upstream = 5 - 1 = 4 km/hr
Let the distance b/w two points = 12 km (LCM of 6 and 4)
Now,
Time taken by boat to go downstream = \(\frac{12}{6}\) = 2 hrs. = 120 min.
Time taken by boat to go upstream = \(\frac{12}{4}\) = 3 hrs. = 180 min.
Total time to go and return = 120 + 180 = 300 min
Hence, ATQ,
Total time = 75 min i.e. \(\frac{1}{4}\)th of 300
Therefore, distance = \(\frac{1}{4}\)th of 12 = 3 km.