GMAT preparation


Data Sufficiency questions pose a special challenge to most GMAT test takers.

Read about the common mistakes in Data Sufficiency questions and learn to avoid them.

The following are the common mistakes test takers make in data sufficiency questions. Some other types exist but are quite rare and can be completely eliminated using good practice material.

  • Forgetting to ignore statement (1) while checking statement (2). This mistake points to answer choice B instead of C.

    At Papertown, all residents buy either newspaper A or newspaper B. How many of the residents of Papertown bought newspaper B?

    (1) Of the 125 Papertown residents, 20% bought newspaper B.
    (2) 87 people bought newspaper A.

    Here, the number of residents is supplied in statement (1) only, and not in the question itself. When checking statement (2) alone, some test takers apply the total number of residents supplied in the first statement (125) to the second statement to conclude that 38 people (125-87) bought newspaper B.
    However, the total number of residents given in the first statement must not be used for the second statement. The answer should be A and not D.

  •  A statement that proves that the question is incorrect is sufficient to answer the question. Yes or no are legitimate answers. This error might lead to the conclusion that the statement is not sufficient when it is.

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