If a boat is rowed downstream for 96 km in 3 hours and upstream for 88 km in 11 hours, what is the speed of the boat and the river?  Answers
A) 12 , 20  B) 20 , 20  C) 20 , 11  D) 20 , 12  E) 12 , 12

Rationale: explanation : if x : speed of boats man in still water y : speed of the river downstream speed ( ds ) = x + y upstream speed ( us ) = x â € “ y x = ( ds + us ) / 2 y = ( ds â € “ us ) / 2 in the above problem ds = 32 ; us = 8 x = ( 32 + 8 ) / 2 = 40 / 2 = 20 km / hr y = ( 32 - 8 ) / 2 = 24 / 2 = 12 km / hr answer : d
Answer: D