A man can swim in still water at 9 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is?  Choose the correct answer.
A) 3.9	B) 4.2	C) 5.3	D) 1.5	E) 3
M = 9   S = x   DS = 9 + x   US = 9 - x   9 + x = (9 - x)2   9 + x = 18 -2x   3x = 9   x = 3   Answer:3
<result>E</result>
A man can swim in still water at 9 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is?