Question 921946
You paddle 12 miles downstream, with a 2 mph current, in one hour less than you can paddle 10 miles upstream against the current. What would their average speed be when there is no current?
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let x=ave speed when there is no current(still water)
x+2=speed downstream
x-2=speed upstream
travel time=distance/speed
..
10/(x-2)-12/(x+2)=1
lcd:(x+2)(x-2)
10(x+2)-12(x-2)=(x+2)(x-2)
10x+20-12x+24=x^2-4
x^2+2x-48=0
(x+8)(x-6)=0
take positive root
x=6
ave speed when there is no current=6 mph