SOLUTION: If a boat travels downstream for one hour and travels twelve miles and returns upstream to the starting point and the trip requires four hours how fast is the current

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Question 316631: If a boat travels downstream for one hour and travels twelve miles and returns upstream to the starting point and the trip requires four hours how fast is the current
Found 2 solutions by ankor@dixie-net.com, mananth:
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
If a boat travels downstream for one hour and travels twelve miles and returns
upstream to the starting point and the trip requires four hours how fast is the current
:
Let s = speed of boat in still water
Let c = speed of the current
:
Write a distance equation for each trip:
1(s + c) = 12
4(s - c) = 12
:
Simplify the second equation; divide by 4, subtract from the 1st equation
s + c =12
s - c = 3
-----------subtraction eliminates s, find c
2c = 9
c = 9%2F2
c = 4.5 mph is the current
:
:
:
Check solution, find the speed of the boat
s + 4.5 = 12
s = 12 - 4.5
s = 7.5 mph speed of the boat
Check solution in the return equation
4(7.5 - 4.5) =
4(3) = 12

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
let speed of current be x mph
..
speed downstream = 12 mph
speed in still water = 12-x
speed upstream = 12-2x
..
time taken down stream = 1 hour
time taken upstream = 3 hours
..
distance = speed * time
distance upstream + distance down stream = total distance
..
12+3(12-2x)=24
12+36-6x=24
12+36-24=6x
24=6x
x=4 mph