Data sufficiency basics
57 flashcards covering Data sufficiency basics for the GMAT Quantitative section.
Data sufficiency questions on the GMAT ask you to determine whether the information provided is enough to answer a problem, without actually solving it. You'll get a question followed by two statements, and your task is to evaluate if one, both, or neither of those statements supplies the necessary data. This format tests your logical reasoning and ability to identify what's truly required, rather than just crunching numbers.
In the GMAT Quantitative section, data sufficiency appears as a key question type, often mixed with problem-solving items, and it can cover topics like algebra, geometry, or statistics. Common traps include assuming extra facts not stated, confusing the statements' individual contributions, or spending time calculating when you should be assessing sufficiency. Focus on evaluating each statement on its own and then together, while keeping track of the question's exact requirements to avoid wasted effort.
A helpful tip: Practice by noting exactly what information is needed before looking at the statements.
Terms (57)
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What is Data Sufficiency?
Data Sufficiency is a question type on the GMAT that asks whether the given statements provide enough information to answer a question, without requiring you to solve it fully, focusing instead on evaluating the sufficiency of each statement alone and together.
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Purpose of Data Sufficiency questions
The purpose is to test your ability to analyze information efficiently and determine what data is necessary to solve a problem, emphasizing logical reasoning over computation.
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The two statements in DS
In Data Sufficiency, two statements follow the question, and you must assess whether statement (1) alone, statement (2) alone, or both together provide sufficient data to answer the question.
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Statement (1) alone sufficient
This means that only the information in statement (1) is enough to answer the question, regardless of statement (2), which is a common evaluation in DS problems.
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Statement (2) alone sufficient
This indicates that only the information in statement (2) is adequate to solve the question, without needing statement (1), as per DS answer choices.
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Both statements together sufficient
When neither statement alone works, but combining the information from both statements provides enough data to answer the question accurately.
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Answer choice A in DS
Answer choice A means statement (1) alone is sufficient to answer the question, but statement (2) alone is not, based on the standard GMAT DS format.
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Answer choice B in DS
Answer choice B indicates that statement (2) alone is sufficient, but statement (1) alone is not, helping to distinguish DS options.
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Answer choice C in DS
Answer choice C is selected when neither statement alone is sufficient, but both statements together provide enough information to solve the problem.
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Answer choice D in DS
Answer choice D applies when each statement alone is sufficient to answer the question, making both (1) and (2) independently adequate.
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Answer choice E in DS
Answer choice E means that even when both statements are considered together, they do not provide enough information to answer the question definitively.
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Strategy: Evaluate statements independently
Always assess statement (1) on its own first, then statement (2) on its own, before combining them, to avoid unnecessary overlap in DS analysis.
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Strategy: Don't solve the problem
In DS, focus on determining if the statements allow you to find a definitive answer, not on calculating the actual value, to save time during the exam.
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Common trap: Assuming extra information
A frequent error is adding assumptions not stated in the problem or statements, which can lead to incorrect sufficiency judgments in DS questions.
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Common trap: Overlooking constraints
Failing to consider restrictions like positive numbers or integer values in the statements can result in mistakenly deeming data insufficient.
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Handling inequalities in DS
For inequalities, check if the statements define a clear range or boundary that answers the question, such as determining if a value is greater than another.
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Handling equations with variables in DS
Determine if the equations from the statements can be solved for the required variables, ensuring you have as many independent equations as unknowns.
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Absolute values in DS
Absolute values may create multiple cases, so statements must resolve all possible scenarios to be sufficient for questions involving distances or deviations.
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Geometry in DS
In geometry problems, statements need to provide enough details about shapes, angles, or lengths to apply theorems and confirm the question can be answered.
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Word problems in DS
For word problems, translate statements into mathematical terms and verify if they yield a unique solution, such as for rates or mixtures.
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Percentages in DS
Statements must provide base values or ratios to calculate percentages accurately, ensuring no ambiguity in the final percentage outcome.
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Ratios and proportions in DS
Check if statements give enough information to set up and solve proportional relationships, like part-to-whole ratios, without additional assumptions.
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Sequences and series in DS
Statements need to specify the pattern, first term, or common difference to determine a specific term or sum in arithmetic or geometric sequences.
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Functions in DS
For functions, ensure statements define the domain, range, or specific values that allow evaluation at the required points.
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Probability in DS
Statements must clarify the sample space and favorable outcomes to calculate a probability, avoiding any undefined events.
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Permutations and combinations in DS
Verify if statements provide the necessary counts of items and conditions to compute arrangements or selections uniquely.
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Overlapping sets in DS
For sets, statements should resolve overlaps using principles like inclusion-exclusion to find exact unions or intersections.
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Example: Simple algebra DS
In a question asking for the value of x in an equation, if statement (1) gives x + 2 = 5, it is sufficient alone since it solves to x = 3.
Question: Is x even? Statement (1): x + 2 = 5.
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Redundant statements in DS
If both statements provide the same information, evaluate them as if only one is present, which might make one alone sufficient.
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Dependent statements in DS
When statements rely on each other for context, combining them might be necessary, but check if they independently resolve the question.
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Independent statements in DS
Statements that can be evaluated separately without referencing each other often lead to options like A, B, or D.
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Using substitution in DS
Substitute values from statements into the question to test if a definitive answer emerges, especially for algebraic expressions.
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Testing numbers in DS
Plug in numbers that satisfy the statements to see if they consistently answer the question, helping identify sufficiency for variables.
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Avoiding calculation errors in DS
Focus on logical flow rather than precise calculations, as errors in arithmetic can mislead sufficiency assessments.
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Time management in DS questions
Spend no more than 2 minutes per question by quickly evaluating statements and moving on if unsure, to maintain exam pace.
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Identifying if a statement is always true
A statement is sufficient if it guarantees a single answer for all possible scenarios that fit the question's conditions.
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Dealing with 'must be' vs. 'could be'
For DS, statements must ensure the answer 'must be' true, not just 'could be', to confirm sufficiency.
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Zero and negative numbers in DS
Statements need to account for zero or negatives if they affect outcomes, like in inequalities or absolute values.
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Fractions and decimals in DS
Ensure statements provide enough precision for fractions or decimals to yield an exact value or comparison.
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Exponents and roots in DS
Statements must resolve ambiguities in exponents, like positive vs. negative bases, or roots of negative numbers.
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Logarithms in DS
For logarithms, statements should specify bases and arguments to avoid undefined cases and ensure a unique solution.
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Coordinate geometry in DS
Statements need coordinates or equations of lines/shapes to determine distances, slopes, or intersections.
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Distance and midpoint formulas in DS
Apply these only if statements provide the necessary points, ensuring calculations can be performed exactly.
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Area and perimeter in DS
For shapes, statements must supply dimensions or properties that allow computation without ambiguity.
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Volume in DS
Statements should give all required measurements for 3D shapes to calculate volume precisely.
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Statistics: Mean in DS
For mean, statements need the total sum and number of values to confirm if the average can be found.
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Statistics: Median in DS
Statements must provide enough data points, sorted if necessary, to identify the middle value.
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Simple interest in DS
Statements should include principal, rate, and time to calculate interest or future value.
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Compound interest in DS
Ensure statements specify compounding frequency and periods to determine the final amount.
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Work rates in DS
Statements need individual or combined rates to solve for time or workers required.
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Distance-speed-time in DS
For motion problems, statements must provide speed, time, or distance to relate them accurately.
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Mixtures and alligations in DS
Statements should give concentrations or quantities to find mixture ratios or results.
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Profit and loss in DS
Verify if statements provide cost price, selling price, or markups to calculate profit percentages.
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Strategy for yes/no questions
For yes/no DS questions, statements must definitively confirm or deny the condition for all cases.
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Strategy for value questions
In value questions, ensure statements allow calculation of a specific numerical answer.
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When statements are sufficient together but not alone
This occurs when each statement lacks key information, but together they complement each other to resolve the question.
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Final tip: Practice with official questions
Regular practice with real GMAT DS questions helps recognize patterns and improve accuracy in sufficiency judgments.