A man swims downstream 40 km and upstream 16 km taking 4 hours each time, what is the speed of the man in still water? Choices
A) 7	B) 7.5	C) 6.8	D) 7.8	E) 8.0
40 --- 4 DS = 10   ? ---- 1   20 ---- 4 US = 5   ? ---- 1 M = ?   M = (10 + 5)/2= 
<gadget id="calculator">(10 + 5)/2</gadget>
<output>15/2 = around 7.5</output>
7.5   Answer: 7.5
<result>B</result>
A man swims downstream 40 km and upstream 16 km taking 4 hours each time, what is the speed of the man in still water?