Question 24531: HERE IS THE PROBLEM:
It takes Lynnette 2 hours to row her boat 9 miles traveling with the current, and 6 hours to return that same distance against the curent. Find her speed and the speed of the current.
I HAVE NEVER HAD TO FIND THE SPEED OF BOAT AND SPEED OF CURRENT TOGETHER IN THE SAME PROBLEM. I DON'T KNOW WHERE TO START. THIS IS DUE BY 01/17/06. THANKS FOR YOUR HELP!
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! the beauty of maths or the power of maths is that you learn the basic approach, the basic methods and then you can learn to apply those to harder situations.
Let speed of boat = x mph
Let speed of current = y mph
So, with the current:
her speed will be x+y. Takes 2 hours to go 9 miles.
Speed = distance/time so
x+y = 9/2
--> x+y = 4.5
and against the current:
her speed will be x-y. Takes her 6 hours to go the same 9 miles.
Speed = distance/time so
x-y = 9/6
--> x-y = 1.5
So, we have 2 unknowns and 2 equations. This is solveable.
x+y = 4.5
x-y = 1.5
Add them together... 2x = 6 --> x = 3mph
So, x+y = 4.5
then 3+y = 4.5
--> y = 1.5 mph
So, her speed is 3mph and river is 1.5 mph
Check in second equation, to makes sure:
x-y = 1.5
3-1.5 is indeed equal to 1.5, so correct
jon.
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