Data Sufficiency / Statement Evaluation
True / False / Cannot-say judgements from given data.
This page is a sequence, not a document: try a question cold, learn the methods, drill until they’re automatic, then prove it under a clock. Skipping straight to reading is the least effective thing you can do here — that’s not opinion, it’s the testing effect.
Try one first
Before any teaching — a real question tells you honestly where you stand.
| Department | Staff |
|---|---|
| Logistics | 20 |
| QA | 45 |
| Packing | 85 |
| Assembly | 50 |
Using the table, is this True, False, or Cannot say? Statement: More than half of Packing's staff are aged under 30.
The methods
Every data sufficiency / statement evaluation pattern the tests use — the method in a few lines, then a worked example.
Statement evaluation
Compute the quantity the statement claims from the exhibit, then judge True or False. 'Cannot say' applies only when the data needed is genuinely not shown.
Worked example
Based on the table, decide: ‘North region sales were more than double South region sales.’
Answer: True
Double South = 2 × 450 = 900. North = 920, which is more than 900, so the statement is True. (Both figures are shown, so 'Cannot say' does not apply.)
Cannot say
Check whether the exhibit actually contains the data the statement needs. If it isn't derivable from what's shown, the answer is Cannot say — not False.
Data sufficiency
Test each statement alone for whether it pins down the answer, then both together; choose the matching sufficiency option.
Worked example
Is the number x greater than 50? (1) x is greater than 40. (2) x is a multiple of 30.
Answer: Both together are sufficient, but neither alone
Statement (1): x could be 45 (≤50) or 60 (>50) — insufficient. Statement (2): x could be 30 or 60 — insufficient. Together: x>40 and a multiple of 30 means x is 60, 90, … always > 50 — sufficient. So BOTH together, neither alone.
Quantity comparison
Evaluate both quantities exactly, then compare; pick 'cannot determine' only if the relationship genuinely varies.
Worked example
Column A: 25% of 80. Column B: 80% of 25. Which is greater?
Answer: The two quantities are equal
Column A = 0.25 × 80 = 20. Column B = 0.80 × 25 = 20. They are equal — 'a% of b' always equals 'b% of a'. The trap is assuming the larger percentage wins.
Drill it
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Prove it under a clock
A skill isn't test-ready until it survives time pressure, mixed with everything else.
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