SOLUTION: A boat travels 45 kms. upstream and then returns to the dock traveling 45 kilometers downstream. The speed of the boat in still water is 12 km/hr. The total time for the trip is 8

Question 939724: A boat travels 45 kms. upstream and then returns to the dock traveling 45 kilometers downstream. The speed of the boat in still water is 12 km/hr. The total time for the trip is 8 hours. Find the speed of the current.
I got the answer to be the current = 3 km/hr. Is this correct?
Thank you!
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
A boat travels 45 kms. upstream and then returns to the dock traveling 45 kilometers downstream. The speed of the boat in still water is 12 km/hr. The total time for the trip is 8 hours. Find the speed of the current.
***
let c=speed of current
12+c=speed of boat downstream
12-c=speed of boat upstream
Travel time=distance/speed
..

lcd:(12-c)(12+c)
45(12-c)+45(12+c)=8(12-c)(12+c)
540-45c+540+45c=8(12^2-c^2)
1080=8(144-c^2)
1080=1152-8c^2
8c^2=72
c^2=9
c=3
speed of current=3 km/hr
congratulations! You got it right.
RELATED QUESTIONS
The current in a stream moves at a speed of 3 mph. A boat travels 45 mi upstream and 45... (answered by nerdybill)

a cruise boat travels 24 miles downstream in 3 hours and returns to its starting point... (answered by stanbon,checkley71)

A cruise boat travels 60 miles downstream in 3 hours and returns to its starting point... (answered by orca)

#2 A CRUISE BOAT TRAVELS 96 MILES DOWNSTREAM IN 4 HOURS AND RETURNS TO ITS STARTING POINT (answered by ankor@dixie-net.com)

a cruise boat travels 96 miles downstream in 2 hours and returns to its starting point... (answered by checkley77)

A cruise boat travels 36 miles downstream in 4 hours and returns to its starting point... (answered by FrankM)

A cruise boat travels 96 miles downstream for 2 hours and returns to its starting point... (answered by stanbon)

#1: The speed of a stream is 6mph If a boat travels 54 miles downstream in the same... (answered by ewatrrr)

The current in a stream moves at a speed of 3mph. A boat travels 45mi upstream and 45 mi... (answered by checkley77,dabanfield)