Selection based questions are a regular set of question types which are commonly seen in most exams. The questions generally consist of a group of people/ objects that have to be put together in teams, or selected together- albeit with a set of constraints/ conditions about certain people/ objects who need to be put together/ cannot be put together. 

The important points while solving selection – based questions are:

• The ability to visualise the structure of the selected teams to be formed, including the number of people/ objects in each team
• The ability to create symbolic representations of the various clues provided so that you can bring together each of the relevant clues while selection
• The ability to wait for and reach the appropriate time in the problem-solving question from where the indirect clues providing in the question can be used

Selection Type Questions

Rashmi wants to take four courses this semester. There are only seven courses in which she is interested: three major science courses- Zoology, Botany and Chemistry; and four optional courses- Political Science, Psychology, Mathematics and Economics. To meet college requirements, she must take two major science courses. There are some scheduling problems: Political Science overlaps both Botany and Mathematics but she can choose Botany and Mathematics as two different courses. Zoology is given at the same time as Psychology.

• If Rashmi decides she will take International Finance, what will her other three courses be?

1. Zoology, Chemistry and Botany
2. Zoology, Chemistry and Economics
3. Zoology, Chemistry and Psychology
4. Chemistry, Botany and Economics  

• If Rashmi takes four courses this semester, then which of the following statements is not possible?

1. She takes Psychology and does not take Botany.
2. She takes Mathematics and does not take Botany.
3. She takes Political Science and does not take Chemistry.

1. I only
2. II only
3. III only
4. I and III only

Solution:

• It can be seen that if Rashmi takes Political Science, she would not be able to take the Botany and Mathematics course. This means that she has to choose Zoology and Chemistry as her two major science courses and because Zoology overlaps with Psychology, her second optional course must be Economics. Option b) is correct.
• Statement I is definitely not possible because if takes Psychology she cannot take Zoology and she must have to take Botany. Statement II is possible, while statement III can be seen to not be possible as if she takes Political Science, she has to take Chemistry as Botany would not be available to her. Option d) is correct.

Let’s look at another question

Seven people, specialists in different fields are A, B, C, D, E, E, G. They visit the office four days a week- Monday, Tuesday, Wednesday AND Thursday. At least one but not more than two people visit the office on each of these days. Each is a specialist in different fields- Medicine, Law, Sales, Engineering, Teaching, Business and Research.

• D visits on Wednesday and is a specialist in Research.
• The Engineer doesn’t not visit on Thursday, neither with E nor with G.
• The Researcher F visits alone on Monday.
• B visits on Tuesday and is not an Engineer.
• C visits on Tuesday. G is not a Businessman.
• The Engineer visits with the Doctor.
• The Sales specialist visits on Wednesday.
• A is neither a Lawyer nor a Researcher.

• What is A’s speciality?

1. Teaching
2. Medicine
3. Engineering
4. Data inadequate

• On which day does E visit?

1. Tuesday
2. Thursday
3. Tuesday or Thursday
4. Wednesday

Solution

From the first clue, the two people visiting on Wednesday are D and the other is a Businessman. From clue three, F is a Research specialist and visits alone on Monday. From clue seven, the Sales specialist visits on Wednesday. This means that D is a specialist in Sales.

Moving onto clues four and five we get that B and C visit on Tuesday and from clue six the Engineer visits with the Doctor. They either visit on Tuesday or Thursday. From clue two we get that B is a Doctor and C is the Engineer. From clue five, G is not a Businessman and does not visit on Wednesday. Hence, G visits on Thursday. From clue eight we get that A also visits on Thursday.

The only person left is E who is a Businessman. Also, since A is not a Lawyer, G is a Lawyer and A is a Teacher.

Summarising in a table, we get

1. Option a) is correct.
2. Option d) is correct.