Speed of a boat in standing water is 18 kmph and the speed of the stream is 3 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-

Question: Speed of a boat in standing water is 18 kmph and the speed of the stream is 3 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-

Solution:
Given,
Speed of a boat in standing water = 18 kmph
The speed of the stream = 3 kmph

∴ Speed upstream = (18 - 3) kmph
= 15 kmph.

∴ Speed downstream = (18 + 3) kmph
= 21 kmph.

So, Total time taken = (105/15 ) + (105/21) hours
= (7 + 5) hours
= 12 hour