The speed of a boat in still water is 10km/hr. If it can travel 26km downstream and 14 km upstream in same time, the speed of the stream is :

Question: The speed of a boat in still water is 10km/hr. If it can travel 26km downstream and 14 km upstream in same time, the speed of the stream is :

Solution:
The speed of boat in still water is 10 km/hr.
Let, Speed of stream be x km/hr.
Upstream speed = (10 - x) km/hr.
Downstream speed = (10 + x) km/hr.

According to the question,
26/(10 + x) = 14/(10 - x)
⇒ 26 (10 - x) = 14 (10 + x)
⇒ 260 - 26x = 140 + 14x
⇒ 26x + 14x = 260 - 140
⇒ 40x = 120
⇒ x = 120/40
∴ x = 3 km/hr

∴ Speed of stream is 3 km/hr.