<PRE><B>Question 1048257</B>
velocity * time=distance; x=current velocity in mph
(34 mph+x)*time=100 miles
time=100/(34+x)
time =(80)/(34-x), going upstream
These times are equal so set the other sides equal to each other.

100/(34+x)=(80)/(34-x)
cross-multiply
2720+80x=3400-100x
180x=680
x=3.78 mph ANSWER (3 7/9 exact)
37.78 mph downstream and takes 2.65 hr. 
30.22 mph or 30 7/9 mph upstream and takes 2.65 hrs.
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