Nine large hoses can fill a swimming pool in four hours and six small hoses can fill the same swimming pool in eight hours.How long will it take four large hoses and eight small hoses working together to fill the swimming pool?
4/9 of the large hose will take 9/4 of the time 9/4 * 4 hrs = 9 hours/pool = 1/9 pool /hrs
8 small hoses will take 6/8 of the time 6/8 * 8 hrs = 6 hrs/pool = 1/6 pool /hrs
1 pool/ (1/9 + 1/6) = 3.6 hrs
