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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 : 

A new one-way road is built from M to N. Each car now has three possible routes to travel from A to B: A-M-B, A-N-B and A-M-N-B On the road from M to N, one car takes 7 minutes and each additional car increases the travel time per car by 1 minute. Assume that any car taking the A-M-N-B route travels the A-M portion at the same time as other cars taking the A-M-B route, and the N-B portion at the same time as other cars taking the A-N-B route.
 

If all the cars follow the police order, what is the minimum travel time (in minutes) from A to B? (Assume that the police department would never order all the cars to take the same route.) 

Option: 1

26


Option: 2

32


Option: 3

29.9


Option: 4

30


Answers (1)

best_answer
  • If 1 car is ordered to take the A-M-B route, then the travel time for the car is 12 + 20 = 32 minutes.
  • If 2 cars are ordered to take the A-M-N-B route, then the travel time for each car is 12 + 8 + 12 = 32 minutes.
  • If 1 car is ordered to take the A-N-B route, then the travel time for the car is 20 + 12 = 32 minutes.

As you can see, the travel time is the same for each route. Therefore, the minimum travel time is 32 minutes.

Below table shows the travel times for each route:

    Route

    Travel time for 1 car

    A-M-B

    12 + 20 = 32 minutes

    A-M-N-B

    12 + 8 + 12 = 32 minutes

    A-N-B

    20 + 12 = 32 minutes

As you can see, the travel time is the same for each route. Therefore, the minimum travel time is 32 minutes.

 

Posted by

Rishabh

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