CAT Scheduling Sets: DILR Strategy

Scheduling/order appeared repeatedly through training schedules, train movement, visits, event sequencing and resource-allocation sets. Treat this as a set family, not a promise that CAT will allocate a fixed number of questions to it. The useful preparation is learning how to represent the information and recognise when the set is worth your time.

What this set family usually requires

Core skills include Time slots, precedence, availability, sequencing, overlap, and resource constraints, earliest/latest positions. Before calculation, compress the story into the smallest useful structure—a grid, table, timeline, graph or cases.

A practical solving sequence

Create time grid; place fixed events; convert 'before/after/not together' to constraints; use earliest/latest windows; branch only on bottleneck choices.

The order matters. Many DILR attempts become slow because students create too many cases before using the strongest fixed constraints. A good representation should make deductions easier; if your diagram is becoming more complicated than the paragraph, redraw it.

Should you select this set in a mock?

Prefer when many fixed/predecessor constraints exist; avoid first-pass sets with many interchangeable schedules and weak anchors.

Set selection is part of the skill. During review, compare the set you chose first with the set you *should* have chosen first. That single metric often explains a large part of DILR volatility.

Common time-wasting traps

• Treating 'before' as immediately before
• ignoring duration
• overlap errors
• failing to update availability after case split

Original practice seed

Six training sessions across three days, two rooms, precedence and instructor constraints—find feasible schedules. Build the representation first, then write 3–4 questions yourself: one direct, one conditional, one count/maximum-minimum and one “which must be true” style. Creating questions forces you to see the structure more deeply than passive solution reading.

Mastery checkpoint

Can derive feasible windows for each entity before enumerating complete schedules.

Practise this family until the representation becomes fast, then mix it with unrelated set types. CAT does not announce “this is an arrangement set”; your real advantage comes from recognising the structure under unfamiliar wording and deciding quickly whether it deserves 10–12 minutes of your section.