Why This Topic Matters
Quantitative Reasoning Sets
The DILR sets where the logic is arithmetic: a defined quantity (an index, a weighted average, an occupancy factor, a vote share), a part-filled table, and questions that make you run the definition forwards and backwards. No exotic math — the challenge is bookkeeping under time pressure.
| The tested form | Year | What it looked like |
|---|---|---|
| Weighted-average / factor set | 2025 | An "occupancy factor" defined per train segment; compute and invert it |
| Geometry-flavoured DI | 2024 | Quantities tied to areas/lengths read off a figure |
| Scenario-payoff set | 2024 | An election where vote shares followed stated formulas, case by case |
The method
- Extract the definition. Write the defining formula in symbols before reading question 1. E.g. , .
- Map the data to the symbols. Mark which cells of the table are given and which are unknown.
- Use totals as equations. Row sums, column sums, and "overall average" statements are linear equations — often enough to pin every blank.
- Forwards, then backwards. Early questions apply the definition; later ones invert it ("what must X have been so that…"). Inverting is the same formula, solved for a different symbol.
- Keep units honest. Thousands vs units, percentages vs counts — every recent set mixes them deliberately.
A worked mini-set
A metro line has segments P–Q, Q–R, R–S with capacities 200, 250, 200. The occupancy factor of a segment = passengers carried ÷ capacity. Given: factor(P–Q) = 0.70, passengers(Q–R) = 200, factor(R–S) = 0.55.
- Apply forwards: passengers(P–Q) ; factor(Q–R) ; passengers(R–S) .
- Invert: "What would R–S's factor be if 30 more passengers boarded?" → .
- Totals as equations: "Across all three segments the line carried…" → — one addition, three questions' worth of value.
Common traps
Dividing by the wrong base. Weighted-average sets live and die on the denominator: occupancy uses capacity of that segment, vote share uses votes cast, not electorate, an index uses its own weights. Before computing, say the denominator out loud. CAT writes the definition precisely — the trap options are what you get with the plausible but wrong base.
- Mixing units — thousands in one table, raw counts in another.
- Recomputing instead of reusing — the definition and the totals you've already derived answer most later questions in one step.
Checklist
- Write the defining formula in symbols first
- Mark given vs unknown cells; turn totals into equations
- Say the denominator before every division
- Reuse earlier results — later questions build on them
- Watch units (thousands, %, counts) on every figure
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