Four cars need to travel from Akala (A) to Bakala (B). Two routes are available, one via Mamur (M) and the other via Nanur (N). The roads from A to M, and from N to 8, are both short and narrow. In each case, one car takes 6 minutes to cover the distance, and each additional car increases the travel time per car by 3 minutes because of congestion. (For example, if only two cars drive from A to M, each car takes 9 minutes.) On the road from A to N, one car takes 20 minutes, and each additional car increases the travel time per car by 1 minute. On the road from M to B, one car takes 20 minutes, and each additional car increases the travel time per car by 0.9 minute.
The police department orders each car to take a particular route in such a manner that it is not possible for any car to reduce its travel time by not following the order, while the other cars are following the order.
Question : How many cars would be asked to take the route A-N-B, that is Akala-Nanur-Bakala route, by the police department?
2
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Below can be inferred:
Here is a table showing the travel times for each route:
Route |
Travel time for 1 car |
Travel time for 2 cars |
A-M-B |
6 minutes + 3 minutes/car * (number of cars - 1) |
12 minutes + 6 minutes/car * (number of cars - 1) |
A-N-B |
20 minutes + 1 minute/car * (number of cars - 1) |
40 minutes + 2 minutes/car * (number of cars - 1) |
As you can see, the travel time for each route is nearly the same. Therefore, it is optimal to send 2 cars through each route.
In addition, if 3 cars were directed to go through any of the routes, one of the 3 cars could break the police order and reduce its travel time. For example, if 3 cars were directed to go through route A-M-B, one of the cars could take route A-N-B instead and save 3 minutes.
Therefore, the police department would ask 2 cars to take the route A-N-B.