A motor boat whose speed is 18 km/h in still water takes 1 hour more to go 24 km upstream
Given, speed of the boat in still water = 18 km/hr.
Let the speed of the stream be x km/hr.
Speed of the boat upstream = Speed of boat in still water – Speed of the stream
∴ Speed of the boat upstream = ( 18 – x ) km/hr
Speed of the boat downstream = Speed of boat in still water + Speed of the stream
∴ Speed of the boat downstream = ( 18 + x ) km/hr
Time of upstream journey = Time for downstream journey + 1 hr
⇒ 48x = 324 – x2
⇒ x2 + 48x – 324 = 0
∴ x = 6 (Speed of the stream cannot be negative)
Thus, the speed of stream is 6 km/hr.