A man swims downstream 90 km and upstream 55 km taking 5 hours each time; what is the speed of the current?  Choose one:
A) 3.8
B) 3.5
C) 3.3
D) 3.2
E) 1.6
90 --- 5 DS = 18   ? ---- 1   55 ---- 5 US = 11   ? ---- 1 S = ?   S = (18 - 11)/2= 
<gadget id="calculator">(18 - 11)/2</gadget>
<output>7/2 = around 3.5</output>
3.5   Answer: 3.5
<result>B</result>
A man swims downstream 90 km and upstream 55 km taking 5 hours each time; what is the speed of the current?