Vijay rows a boat 80 km along the stream in 1 hour 20 minutes. Given that his rowing speed in still water is 45 km/hr, in how much time will he cover the same distance against the stream?

2 hours 40 minutes

Let,

Speed of boat in still water be x = 45 km/hr

Speed of stream/ current be y

Downstream speed i.e. x + y = \(\frac{80 }{4/3 }\) = 60 km/hr

Speed of current i.e. y = 60 - 45 = 15 km/hr

Upstream speed i.e. x - y = 45 - 15 = 30 km/hr

Time = \(\frac{80 }{30 }\) = 2 hour 40 min