GMAT® Practice - Data Sufficiency

Concept: Logical Reasoning in Data Sufficiency.

This question is a data sufficiency question focusing on finding whether relation between two people can be established based on information given in the statements.

Directions for Data Sufficiency

This data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements, plus your knowledge of mathematics and everyday facts (such as the number of days in a leap year or the meaning of the word counterclockwise), you must indicate whether -

  1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
  2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
  3. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
  4. EACH statement ALONE is sufficient to answer the question asked.
  5. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.
Numbers

All numbers used are real numbers.

Figures

A figure accompanying a data sufficiency question will conform to the information given in the question but will not necessarily conform to the additional information given in statements (1) and (2).

Lines shown as straight can be assumed to be straight and lines that appear jagged can also be assumed to be straight.

You may assume that the positions of points, angles, regions, etc. exist in the order shown and that angle measures are greater than zero.

All figures lie in a plane unless otherwise indicated.

Note

In data sufficiency problems that ask for the value of a quantity, the data given in the statement are sufficient only when it is possible to determine exactly one numerical value for the quantity.

Question: How is Bill related to Betty?

  1. Cindy, the wife of Bill's only brother Chris does not have any siblings.
  2. Betty is Cindy's brother in law's wife.

Explanatory Answer

Video explanation will be added soon

What kind of an answer will the question fetch?

The question is the equivalent of a What is question though it starts with "How is". Reword it as "What is the relation between Bill and Betty?". Answer to the question should give us an unambiguous relation between Bill and Betty.

When is the data sufficient?

The data is sufficient if we are able to get a UNIQUE answer from the information given in the statements.

Statement 1 Alone: Cindy, the wife of Bill's only brother Chris does not have any siblings.

We know that Cindy has no siblings and she is the wife of Bill's only brother Chris. So, this statement has helped us establish the relation between Cindy and Bill. However, this statement does not provide any information about Betty and is hence not sufficient to answer the question.

  Statement 1 ALONE is NOT sufficient.

Eliminate choices A and D.

Statement 2 Alone: Betty is Cindy's brother in law's wife.

We know that Betty is Cindy's brother in law's wife. This statement establishes a relation between Cindy and Betty. This does not answer the question of how Bill is related to either Cindy or Betty.

  Statement 2 ALONE is NOT sufficient.

Eliminate choice B.

Statements Together: Cindy, the wife of Bill's only brother Chris does not have any siblings. & Betty is Cindy's brother in law's wife.

We combine the two statements, we know that Bill and Cindy are related to each other through Chris, who is the only brother of Bill and that Cindy is Betty's brother in law's wife.

Cindy does not have any siblings and hence her brother in law has to necessarily be her husband's sibling. As Chris is the only brother of Bill, Cindy's brother in law has to be Bill and Betty is his wife.

  Statements TOGETHER are SUFFICIENT.

Choice C is the answer.

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