Question 274655: 1) A boat's speed on its speedometer read 18 miles/hour going downstream, and it reaches its destination in 1.25 hours. the return trip takes 1.75 hours at 18 miles/hours on the speedometer. Find the speed of the current.
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! A boat's speed on its speedometer read 18 miles/hour going downstream, and it reaches its destination in 1.25 hours.
the return trip takes 1.75 hours at 18 miles/hours on the speedometer. Find the speed of the current.
:
Understand that the speedometer will give the boat speed in relation to the water
not to the shore unless the water it perfectly still.
:
Let c = speed of the current
then
(18-c) = speed up stream (in relation to the shore)
and
(18+c) = speed down stream
:
The two trips are equal in distance, write a distance equation. (d = time * speed)
:
down dist = up dist
1.25(18+c) = 1.75(18-c)
22.5 + 1.25c = 31.5 - 1.75c
1.25c + 1.75c = 31.5 - 22.5
3c = 9
c = 3 mph is current
:
:
Check solution by finding the distances, they should be equal
1.25(21) = 26.25 mi
1.75(15) = 26.25 also
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