If a river is flowing at a rate of 6 km/hr and a boat's speed in still water is 100% higher than the river's speed, and the boat travels 'd' kilometers downstream in 9 hours, what is the amount of time (in hours) required for the boat to cover (d+24) km upstream?
Speed of a boat in still water = (200/100) × 6 = 12 km/hr According to the question, => d/(12 + 6) = 9 => d = 162 Required time = (162 + 24)/(12 – 6) = 31 hrs
