A man swims downstream 40 km and upstream 30 km taking 5 hours each time, what is the speed of the man in still water?	Choose one:
A) 12 B) 8 C) 36 D) 5 E) 7
40 --- 5 DS = 8   ? ---- 1   30 ---- 5 US = 6   ? ---- 1 M = ?   M = (8 + 6)/2= 
<gadget id="calculator">(8 + 6)/2</gadget>
<output>7</output>
7   Answer: 7
<result>E</result>
A man swims downstream 40 km and upstream 30 km taking 5 hours each time, what is the speed of the man in still water?