Not probability but ...

[DiceyPlay]

Here's a simple question from a basic algebra class that is giving me a tough time.

A barge moves 7 km/h in still water. It travels 45 km up river and 45 km down river in a total of 14 hours. What is the speed of the current?

Can you not only solve but describe the set up as well?

Thanks in advance.

-dp

[BruceZ]

[ QUOTE ]
Here's a simple question from a basic algebra class that is giving me a tough time.

A barge moves 7 km/h in still water. It travels 45 km up river and 45 km down river in a total of 14 hours. What is the speed of the current?

Can you not only solve but describe the set up as well?

Thanks in advance.

-dp

[/ QUOTE ]


d = distance, r = rate, t = time

d = r*t

t = d/r

If c is the speed of the current, the boat moves at a rate of 7+c downstream, and 7-c upstream. Use the above equations to write an expression for the upstream time plus the downstream time, and set this to 14 hours. Solve for c. You should get 2 km/hr.