SOLUTION: A motorboat traveled 35 km upstream on a river and then up an adjacent stream for 18 km, spending 8 hours on the entire trip. The speed of the river�s current was 1 km/hour slower

Question 971067: A motorboat traveled 35 km upstream on a river and then up an adjacent stream for 18 km, spending 8 hours on the entire trip. The speed of the river�s current was 1 km/hour slower than the speed of the stream�s current. Find the speed of the current of the river, if the speed of the motorboat in still water is 10 km/hour.
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
A motorboat traveled 35 km upstream on a river and then up an adjacent stream for 18 km, spending 8 hours on the entire trip. The speed of the river�s current was 1 km/hour slower than the speed of the stream�s current. Find the speed of the current of the river, if the speed of the motorboat in still water is 10 km/hour.
***
let c=speed of river
speed of stream=(c+1)
10-c=speed of motorboat upstream on the river
10-(c+1)=(9-c)=speed of motorboat upstream on adjacent stream
travel time=distance/speed
..

lcd:(9-c)(10-c)
35(9-c)+18(10-c)=8(9-c)(10-c)
315-35c+180-18c=8(90-19c+c^2)
315-35c+180-18c=720-152c+8c^2
8c^2-99c+225
(c-3)(8c-75)=0
c=9.375(reject)
or
c=3
speed of the current of the river=3 km/hr
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