Let the speed of the current be x kmph Rate Downstream = (x + 75) kmph According to the question : 150/(x+75) = 1 hour 40 minutes 150/(x+75) = 5/3 hours 450= 5x + 375 5 x = 450 – 375 X= 15 kmph Rate Upstream = 75 – 15 = 60 kmph Required time = 150/60 = 2 hours 30 minutes