SOLUTION: The current in a stream moves at a speed of 4 km/ h. A boat travels 17 km upstream and 17 km downstream in a total time of 10 hr. What is the speed of the boat in still​ wate

Algebra ->  Length-and-distance -> SOLUTION: The current in a stream moves at a speed of 4 km/ h. A boat travels 17 km upstream and 17 km downstream in a total time of 10 hr. What is the speed of the boat in still​ wate      Log On


   

Question 1057766: The current in a stream moves at a speed of 4 km/ h. A boat travels 17 km upstream and 17 km downstream in a total time of 10 hr. What is the speed of the boat in still​ water?
Answer by jorel555(1290) About Me  (Show Source):
You can put this solution on YOUR website!
Let s be the speed of the boat in still water. Then:
17/(s+4) + 17/(s-4)=10
17(s-4)+17(s+4)=10sē-160
10sē-34s-160=0
5sē-17s-80=0
Using the quadratic formula, i.e. x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+, we get two roots: 6.04626276242 and -2.64626276242. Throwing out the negative result, we get the speed of the boat in still water to be 6.04626 kph. ☺☺☺☺