The ratio between the speed of boat to the current of water is 36 : 5. The boat goes along with the current in 5 hours 10 minutes. It will come back in नाव की चाल और पानी की धारा की चाल में अनुपात 36 : 5 है | नाव धारा की चाल के अनुकूल 5 घंटे 10 मिनट में जाती है | यह वापस आएगी

Let boat speed = 36x and current speed = 5x. Downstream speed = 36x + 5x = 41x. Upstream speed = 36x - 5x = 31x. Time taken is inversely proportional to speed for the same distance. Downstream time = 5 hours 10 minutes = 31/6 hours. Upstream time = Downstream time × (Downstream speed/Upstream speed) = (31/6) × (41/31) = 41/6 = 6 hours 50 minutes. The ratio method avoids calculating x and distance separately - the key insight is that time ratios are inverse of speed ratios.