A man can swim in still water at 5 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is? Choose the correct choice from the following.
A) 1.78  B) 1.667  C) 1.15  D) 1.5  E) 1.2

Rationale: m = 5 s = x ds = 5 + x us = 5 - x 5 + x = ( 5 - x ) 2 5 + x = 10 - 2 x 3 x = 5 x = 1.667 answer : b
Answer: B