SOLUTION: A boat on a river travels downstream between two points, 10 mi apart, in one hour. The return trip against the current takes 2 1/2 hours. What is the boat's speed (in still water

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Question 906476: A boat on a river travels downstream between two points, 10 mi apart, in one hour. The return trip against the current takes
2 1/2
hours. What is the boat's speed (in still water)?
Found 2 solutions by richwmiller, lwsshak3:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
r*t=d
with the current
(r+c)*1=10
(r+c)=10/1
r+c=10
against the current
(r-c)*2.5=10
(r-c)=10/2.5
r-c=4.0
r+c=10
add
r+r=10+4.0
2r=14.0
r=7.0 in still water
7-c=4.0
c=7-4.0
c=3.0 current
check
(7+3)*1=10
10*1=10
10=10
ok
(r-c)*2.5=10
(7-3)*2.5=10
4*2.5=10
10.0=10
ok

Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
A boat on a river travels downstream between two points, 10 mi apart, in one hour. The return trip against the current takes 2 1/2 hours. What is the boat's speed (in still water)?
***
let x=boat's speed (in still water)?
let c=speed of current
x+c=boat's speed downstream
x-c=boat's speed upstream
travel time*speed=distance
..
1*(x+c)=10
2.5*(x-c)=10
..
x+c=10
2.5x-2.5c=10
..
2.5x+2.5c=25
2.5x-2.5c=10
add
5x=35
x=7
boat's speed (in still water)=7 mph