Question

Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:

Answer 1

speed of a boat is 9km/hr
boat's speed in current direction=9+1.5=10.5 km/hr
distance=105 km
time= distance/speed= 105/10.5= 10 hr
boat's speed in opposite direction= 9-1.5=7.5 km/ hr
 distance=105 km
time=105/7.5=14 hr
total time= 14+10=24 hr

Answer 2

Total time taken to go and come would be 24 hrs

1) Distance from starting point = 105 km

Speed of boat in standing water = 9kmph

Speed of stream = 1.5 kmph

2) When going upstream, the resultant speed would be 9-1.5 = 7.5 kmph

Time taken = 105/7.5 = 14 hrs

3) When going downstream, the resultant speed would be 9+1.5 = 10.5 kmph

Time taken = 105/10.5 = 10 hrs.

4) Total time taken to go and come back = 14+10 = 24 hrs