<PRE><B>Question 1170346</B>
x=speed of current
15+x downstream and takes 10/(15+x) units are mi/mi/hr or hr
15-x upstream and takes 5/(15-x) hr
Those two are equal because they are both the same time
Cross-multiply, 150-10x =75+5x
75=15x
x=5 mph
downstream and 20 mph and takes 30 min
upstream and 10 mph and takes 30 min
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