 |
| ||
| |||
|
| Math Central | Quandaries & Queries |
|
The speed of the current in a river is 2mph. Jessica travels 20 miles upstream and then 20 miles downstream in a total time of 5 1/3 hr. Find the speed of the boat. I know you have to use V= d/t, but what is the equation for time because you have to factor in that upstream the boat is slower and downstream the boat is faster? |
Suppose that the speed of the boat is still water is b miles per hour. Thus going upstream her speed is b - 2 miles per hour and hence the time it takes to travel upstream 20 miles is given by time upstream = 20/(b - 2) hours.
Find the time it takes her to travel 20 miles downstream and add the two times to obtain the total time of 5 1/3 hours. This is an equation in b. Solve for b.
I hope this helps,
Penny
| ||
| ||
| ||
 |
 |
|
Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.