If a boat is rowed downstream for 600 km in 20 hours and upstream for 48 km in 4 hours, what is the speed of the boat and the river? Choose the correct choice: A) 21 , 21 B) 9 , 21 C) 21 , 9 D) 9 , 9 E) 20 , 8
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 = 30 ; Us = 12   x = (30 + 12) / 2 = 42/2= 
<gadget id="calculator">42/2</gadget>
<output>21</output>
21 km/hr   y= (30 - 12)/2 = 18/2= 
<gadget id="calculator">18/2</gadget>
<output>9</output>
9 km/hr   ANSWER: 21 , 9
<result>C</result>
If a boat is rowed downstream for 600 km in 20 hours and upstream for 48 km in 4 hours, what is the speed of the boat and the river?