SOLUTION: If a boat travels 30 miles upstream in 4 hours and the trip downstream takes 2.5 hours, what is the rate of the boat in still water? Need help.
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Question 331537: If a boat travels 30 miles upstream in 4 hours and the trip downstream takes 2.5 hours, what is the rate of the boat in still water? Need help. Answer by mananth(16946) (Show Source):
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let speed of boat in still water be xmph
speed of current be y mph
30/(x-y)=4
30=4x-4y.............1
..
30/(x+y)=5/2
60=5x+5y
divide by 5
12=x+y................2
..
multiply equation 2 by 4 and it to equation 1
48+30=4x+4y+4x-4y
78=8x
9.75=x
speed of boat in still water = 9.75 mph
