Qs 1-4: Answer the questions based on the following:

A new airlines company is planning to start operations in a country. The company has identified ten different cities which they plan to connect through their network to start with. The flight duration between any pair of cities will be less than one hour. To start operations, the company has to decide on a daily schedule.

The underlying principle that they are working on is the following:

Any person staying in any of these 10 cities should be able to make a trip to any other city in the morning and should be able to return by the evening of the same day.

Q.1

If the underlying principle is to be satisfied in such a way that the journey between any two cities can be performed using only direct (non-stop) flights, then the minimum number of direct flights to be scheduled is:

A. 45

B. 90

C. 180

D. 135

If a journey is from city X to city Y, then how many values can (X, Y) assume?

For each value of (X, Y), how many flights will be needed so that one may travel one way in the morning and also travel the other way in the evening?

C. 180

Q.2

Suppose three of the ten cities are to be developed as hubs. A hub is a city which is connected with every other city by direct flights each way, both in the morning as well as in the evening. The only direct flights which will be scheduled are originating and/or terminating in one of the hubs. Then the minimum number of direct flights that need to be scheduled so that the underlying principle of the airline to serve all the ten cities is met without visiting more than one hub during one trip is:

A. 54

B. 120

C. 96

D. 60

10 cities are divided into two groups …. the 3 hubs (say group A) and the 7 others (say group B).

How many connections between any two cities of group A?

How many connections between one city of group A and one city of group B?

How many connections between any two cities of group B?

For any pair of cities, how many flights in a day to meet the condition of travel in morning and return in evening?

C. 96

Additional directions for questions 3 & 4: Suppose the 10 cities are divided into 4 distinct groups G1, G2, G3, G4 having 3, 3, 2 and 2 cities respectively and that G1 consists of cities named A, B and C. Further, suppose that direct flights are allowed only between two cities satisfying one of the following:

  1. Both cities are in G1
  2. Between A and any city in G2
  3. Between B and any city in G3
  4. Between C and any city in G4

Q.3

Then the minimum number of direct flights that satisfies the underlying principle of the airline is:

TITA (Type in the answer) Q.

How many pair of cities having flights between them …. satisfying condition 1 i.e. between any two of G1? Satisfying condition 1 i.e. between A and any of G2? And so on.

And for a given pair of cities, how many flights to meet the objective of flying one way in the morning and other way in the evening?

40

Additional directions for questions 3 & 4: Suppose the 10 cities are divided into 4 distinct groups G1, G2, G3, G4 having 3, 3, 2 and 2 cities respectively and that G1 consists of cities named A, B and C. Further, suppose that direct flights are allowed only between two cities satisfying one of the following:

  1. Both cities are in G1
  2. Between A and any city in G2
  3. Between B and any city in G3
  4. Between C and any city in G4

Q.4

Due to operational difficulties at A, it was later decided that the only flights that would operate at A would be those to and from B. Cities in G2 would have to be assigned to G3 or to G4.

What would be the maximum reduction in the number of direct flights as compared to the situation before the operational difficulties arose?

TITA type

From the total flights as found in the previous questions, how many pairs of cities connected by a direct flight will be eliminated?

From A, within G1?

From A to one city of G2? Are these flights totally eliminated?

4