1971 AHSME Problems/Problem 18
Problem
The current in a river is flowing steadily at miles per hour. A motor boat which travels at a constant rate in still water goes downstream miles and then returns to its starting point. The trip takes one hour, excluding the time spent in turning the boat around. The ratio of the downstream to the upstream rate is
Solution
Let the boat travel over still water at rate . Then, it travels downstream at rate and upstream at rate . The distance travelled downstream can be expressed as , where is the time taken to travel downstream. Because the total time taken is hour, the distance travelled upstream can be represented as . Because both distances are the same ( miles), we can equate the two expressions to solve for in terms of :
See Also
1971 AHSC (Problems • Answer Key • Resources) | ||
Preceded by Problem 17 |
Followed by Problem 19 | |
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