A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:
1 km/hr
1.5 km/hr
2 km/hr
2.5 km/hr
Explanation:
Suppose he move 4 km downstream in $ x $ hours. Then,
| Speed downstream =$ \left(\dfrac{4}{x} \right) $km/hr. |
| Speed upstream =$ \left(\dfrac{3}{x} \right) $km/hr. |
| $\therefore \dfrac{48}{(4/x)} $+$ \dfrac{48}{(3/x)} $= 14 or $ x $ =$ \dfrac{1}{2} $. |
So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.
| Rate of the stream =$ \dfrac{1}{2} $(8 - 6) km/hr = 1 km/hr. |