A boy swims downstream 48 km and upstream 12 km taking 6 hours each time; what is the speed of the current? Choose the correct answer:
A) 1  B) 2  C) 3  D) 4  E) 5
48 --- 6 DS = 8   ? ---- 1   12 ---- 6 US = 2   ? ---- 1 S = ?   S = (8 - 2)/2= 
<gadget id="calculator">(8 - 2)/2</gadget>
<output>3</output>
3   Answer: 3
<result>C</result>
A boy swims downstream 48 km and upstream 12 km taking 6 hours each time; what is the speed of the current?