Question 1145946
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A boat traveled downstream a distance of 90 mi and then came right back. If the speed of the current was 20 mph 
and the total trip took 6 hourscomma nbspfind the average speed of the boat relative to the water.
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With the speed of the current of 20 mph,  it is a mountain river.  Something like a waterfall.


I do not think that boats are able to travel  "upstream"  and even  "downstream"  in such a river.  



If downstream,  then only once,  after which case a boat becomes a  "scrap metal"  (if it was made of metal).



To get some knowledge on the subject,  look into this web-site


https://hypertextbook.com/facts/2006/NervanaGaballa.shtml



Avoid travel at such dangerous conditions (!)