Question

the speed of a boat in still water is 18 km/hr.It can go 48km upstream and return to the original point in 6 hours find the speed of the stream​

Answer 1

Given:

Speed of boat in still water = 18km/hr

Let speed of the stream = s

Speed of boat upstream = Speed of boat in still water - speed of stream = 18−s

Speed of boat down stream = Speed of boat in still water + speed of stream = 18+s

Time taken for upstream = Time taken to cover downstream + 1

⇒SpeedupstreamDistanceupstream=SpeeddownstreamDistancedownstream+1

⇒18−s24=18+s24+1

⇒24(18+s)=24(18−s)+(18−s)(18+s)

⇒s2+48s−324=0

⇒s2+54s−6s−324=0

⇒(s+54)(s−6)=0

⇒s=6,−54

⇒s=−54

Thus, s=6km/hr, Speed of steam cannot be negative.