SOLUTION: Question 400689: A sight seeing boat travels an average speed of 22 mph in the calm water of a large lake. The same boat is used for sight-seeing in a near by river. In the river,

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Question 858907: Question 400689: A sight seeing boat travels an average speed of 22 mph in the calm water of a large lake. The same boat is used for sight-seeing in a near by river. In the river, the boat travels 2.1 downstream (with the current) in the same amount of time it takes to travel 1.7 miles upstream (against the current). Write an equation that can be used to solve the problem and find the current of the river.
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Lookup of that question shows that somebody answered it in that question posting. Be aware, some of the given values there are different from the ones you used in your posting here.

Let c = the speed of the river current.
R*T=D for rate, time, distance, basic uniform travel rate relationship.

________________speed__________time__________distance
DOWNSTRM._______22+c___________t_____________2.1
UPSTREAM________22-c___________t_____________1.7

The two times are described as being equal, and both are t.
Downstream equation will give t=2.1%2F%2822%2Bc%29; and the upstream equation will give t=1.7%2F%2822-c%29.

The two expressions for time being equal,
highlight%282.1%2F%2822%2Bc%29=1.7%2F%2822-c%29%29.

1.7%2822%2Bc%29=2.1%2822-c%29
1.7%2A22%2B1.7c=2.1%2A22-2.1c
1.7c=2.1%2A22-2.1c-1.7%2A22
1.7c%2B2.1c=2.1%2A22-1.7%2A22
3.8c=22%282.1-1.7%29
3.8c=22%280.4%29
3.8c=8.8
c=8.8%2F3.8
highlight%28c=2.31%29 or highlight%28c=2.32%29 ------ this could be done as a rational number result, but the accuracy would not be needed that way.