Question

In a river flowing at 2 km/hr, a boat travels 32 km upstream and then returns downstream to the starting point. If its speed in still water be 6 km/hr. Find the total journey time.

Answer 1

Answer:

12hr

Explanation:

PART-I

Speed of River: 2km/hr downstream

Speed of Boat: 6 km/hr upstream

Effective speed of boat: 4km/hr upstream [(+6)+(-2) = (+4)]

Distance travelled: 32km

Time taken: Distance/Effective Speed = 32/4 = 8hr

PART-II

Speed of River: 2km/hr downstream

Speed of Boat: 6 km/hr downstream

Effective speed of boat: 8km/hr upstream [(-6)+(-2) = (-8)]

Distance travelled: 32km

Time taken: Distance/Effective Speed = 32/8 = 4hr

PART-III

TOTAL TIME TAKEN

=Time taken in PART-I + Time taken in PART-II

=8hr + 4hr  =12hr