SOLUTION: A boat can travel 9 miles upstream in the same amount of time it takes to travel 11 miles downstream. if the current of the river is 3 miles per hour, complete the chart below and

Question 234574: A boat can travel 9 miles upstream in the same amount of time it takes to travel 11 miles downstream. if the current of the river is 3 miles per hour, complete the chart below and use it to find the speed of the boat in still water
distance = rate * Time
upstream 9 r-3
downstream 11 r+3
Found 2 solutions by solver91311, nyc_function:
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

The time is the same for both the upstream and downstream trips ("in the same amount of time"), so just call it .

Since

we can also say

So for the upstream trip:

And for the downstream trip:

But , so we can say:

Just cross-multiply and solve for

John

Answer by nyc_function(2741) (Show Source): You can put this solution on YOUR website!
We need to find the time for the up and down trip.
We use the following equation twice to find the time going up and down: d/r = t

Going Up:
9 = (r + 3)t
9/(r + 3) = t
Going Down:
11 = (r - 3)t
11/(r - 3) = t

I will set up the equation and you can finish.

(r + 3)(9/(r + 3) = (r - 3)(11/(r - 3)
Can you finish now?

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