SOLUTION: a speed boat takes 3 hours longer to go 45 miles up a river than to return. if the boat cruises at 20 mph in still water, what is the rate of the current

Question 887905: a speed boat takes 3 hours longer to go 45 miles up a river than to return. if the boat cruises at 20 mph in still water, what is the rate of the current
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
a speed boat takes 3 hours longer to go 45 miles up a river than to return. if the boat cruises at 20 mph in still water, what is the rate of the current
***
let c=rate of current
20+c=speed of boat down river
20-c=speed of boat up river
travel time=distance/speed

lcd: (20+c)(20-c)

900+45c-900+45c=3(20^2-c^2)=3(400-c^2)=1200-3c^2
90c=1200-3c^2
3c^2+90c-1200=0
c^2+30c-400=0
(c+40)(c-10)=0
c=-40 reject
or
c=10
rate of the current=10 mph
RELATED QUESTIONS
A speedboat takes 4 hours longer to go 80 miles up a river than to return. If the boat... (answered by solver91311)

A speedboat takes 4 hours longer to go 80 miles up a river than to return. If the boat... (answered by Fombitz)

A speedboat takes 4 hours longer to go 80 miles up a river than to return. If the boat... (answered by robertb)

a boat takes 2 hours longer to go 45 miles up a river than to return. If the boat's... (answered by Paul,sgt_spike)

Please HELP! a boat takes 2 hours longer to go 45 miles up a river than to return. If... (answered by venugopalramana)

a boat takes 2 hours longer to go 45 miles up a river than to return. If the boat's speed (answered by AnlytcPhil)

A boat takes 3 hours longer to go 60 miles up a river than to return. If the boat cruises (answered by josmiceli)

an excursion boat takes 1.5 times as long to go 360 miles up a river than to return. If... (answered by lwsshak3)