 |
| ||
| |||
|
| Math Central | Quandaries & Queries |
|
Question from paul, a parent: a boat travels 100 miles downstream in the same length of time it travels 50 miles upstream. if the boat's speed in still water is 30 mph find the speed of the current of the river? |
Hi Paul,
You don't know the speed of the river so I am going to call it s mph. Thus, going with the current, downstream, the speed of the boat is (30 + s) mph and going upstream, against the current, the speed of the boat is (30 - s) mph.
At (30 + s) mph how long does it take to go 100 miles?
At (30 - s) mph how long does it take to go 50 miles?
These two times are the same. Solve for s.
Penny
| ||
| ||
| ||
 |
 |
|
Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.