SOLUTION: Don williams uses his small motorboat to go 5 miles upstream to his favorite fishing spot. Against the current, the trip takes 5/12 hour. With the current the trip takes 1/4 hour.

Question 880566: Don williams uses his small motorboat to go 5 miles upstream to his favorite fishing spot. Against the current, the trip takes 5/12 hour. With the current the trip takes 1/4 hour. How fast can the boat travel in still water. What is the speed of the current.
In still water the boats speed is mph
The speed of the current is mph
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Don williams uses his small motorboat to go 5 miles upstream to his favorite fishing spot.
Against the current, the trip takes 5/12 hour.
With the current the trip takes 1/4 hour.
How fast can the boat travel in still water.
What is the speed of the current.
:
let s = speed in still water
let c = rate of the current
then
(s-c) = effective speed up-stream
and
(s+c) = effective speed down-stream
:
Write a distance equation for each way; dist = time * speed
(s-c) = 5
(s+c) = 5
Get rid of those annoying fractions, mult the 1st eq by 12, the 2n by 4
5(s-c) = 60
s + c = 20
:
5s - 5c = 60
simplify, divide by5, add to the 2nd equation
s - c = 12
s + c = 20
--------------adding eliminates c, find s
2s = 32
s = 16 mph is the boat speed in still water
:
find the speed of the current
16 + c = 20
c = 20 - 16
c = 4 mph is the current
:
;
Check these solutions in the original equation
(16-4) = 5
*12 = 5
and
(16+4) = 5
* 20 = 5

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