Data Sufficiency – Reasoning Concepts

In reasoning-based Data Sufficiency, the question assesses your ability to use information logically to draw conclusions. Typically, the question involves topics like relationships, sequences, rankings, directions, and assumptions. Instead of calculating values, you’re determining if you have enough logical information to answer the question.

Structure of Reasoning-Based Data Sufficiency Questions

Just like in quantitative data sufficiency, reasoning-based questions are presented in this structure:

Question Statement: This is the main problem or condition you’re analyzing.
Two Statements: There are two statements, labeled (1) and (2), that contain specific logical information related to the question.
Options: You select the option that best represents the sufficiency of the statements.

The typical answer choices are:

Option (A): Statement (1) alone is sufficient, but Statement (2) alone is not sufficient.
Option (B): Statement (2) alone is sufficient, but Statement (1) alone is not sufficient.
Option (C): Both statements together are sufficient, but neither statement alone is sufficient.
Option (D): Each statement alone is sufficient.
Option (E): Statements (1) and (2) together are not sufficient.

Types of Reasoning-Based Data Sufficiency Questions

Reasoning-based Data Sufficiency questions often include:

Order and Ranking
Blood Relations
Direction Sense
Logical Deduction

Examples of Reasoning-Based Data Sufficiency Questions

Let’s look at examples for each type with detailed solutions.

1. Order and Ranking

Example 1

Question: Who is taller, Riya or Sameer?
Statements:

(1) Riya is taller than Neha.
(2) Sameer is shorter than Priya, who is taller than Neha.

Solution:

Consider Statement (1):
Statement (1) tells us that Riya is taller than Neha, but we have no information about Sameer’s height, so this is not sufficient.
Consider Statement (2):
Statement (2) tells us that Sameer is shorter than Priya, and Priya is taller than Neha. However, it does not provide information about Riya’s height relative to Sameer, so this is also not sufficient.
Combine Statements (1) and (2):
Even after combining, we know that Riya is taller than Neha and Priya is taller than Sameer, but we still don’t have any direct or indirect comparison between Riya and Sameer.

Answer: Statements (1) and (2) together are not sufficient. (Option E)

2. Blood Relations

Example 2

Question: How is P related to Q?
Statements:

(1) P is the sister of R, who is the son of Q.
(2) Q is the father of R.

Solution:

Consider Statement (1):
Statement (1) says P is the sister of R, and R is the son of Q. This implies Q is a parent of P, but it doesn’t specify the gender of Q, so we can’t determine the exact relation between P and Q. Thus, this statement alone is insufficient.
Consider Statement (2):
Statement (2) says Q is the father of R. While it tells us that Q is male and is the father of R, it does not mention P or clarify their relation.
Combine Statements (1) and (2):
From both statements, we know that P is R’s sister, and Q is R’s father, so we can conclude that Q is also P’s father. This allows us to determine that P is the daughter of Q.

Answer: Both statements together are sufficient, but neither alone is sufficient. (Option C)

3. Direction Sense

Example 3

Question: Is X to the north of Y?
Statements:

(1) X is to the east of Z, and Z is to the north of Y.
(2) Y is to the west of Z.

Solution:

Consider Statement (1):
Statement (1) says X is east of Z and Z is north of Y. This places Z north of Y and X east of Z, but we don’t know if X is north of Y. This statement alone is insufficient.
Consider Statement (2):
Statement (2) tells us that Y is to the west of Z. This information alone doesn’t clarify X’s position relative to Y, so it is also insufficient.
Combine Statements (1) and (2):
Combining both, we know that Z is north of Y, and X is east of Z. However, this does not definitively place X as north of Y since X could be northeast or east of Y.

Answer: Statements (1) and (2) together are not sufficient. (Option E)

4. Logical Deduction

Example 4

Question: Can person A complete a project on time if they start today?
Statements:

(1) Person A has three days left to complete the project.
(2) Person A usually completes similar projects in four days.

Solution:

Consider Statement (1):
Statement (1) tells us there are three days remaining, but we don’t know if this is enough time for A. So, Statement (1) alone is insufficient.
Consider Statement (2):
Statement (2) says that person A usually completes similar projects in four days, but it doesn’t give a deadline or indicate how many days remain, so this alone is also insufficient.
Combine Statements (1) and (2):
Combining both, we know person A typically requires four days but only has three days left. Therefore, A cannot complete the project on time.

Answer: Both statements together are sufficient, but neither alone is sufficient. (Option C)

Tips for Reasoning-Based Data Sufficiency Questions

Stick to Sufficiency: Remember, you’re only determining if the statements provide enough information, not solving the problem in full.

Visualize Relationships: For questions involving directions, relations, or ranking, draw a diagram to help visualize the information.

Isolate Each Statement: Carefully analyze each statement separately before combining them.

Beware of Assumptions: Avoid assuming information not explicitly provided, as this can lead to incorrect conclusions.

Read concepts and formulas for: Direction Sense

Refer Aptitude Questions with Solutions on Data Sufficiency: https://www.learntheta.com/aptitude-questions-data-sufficiency/

Practice Aptitude Questions on Data Sufficiency with LearnTheta’s AI Practice Platform: https://www.learntheta.com/placement-aptitude/

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