CAT Routes & Networks: DILR Strategy

Routes/networks appeared in CAT 2022, 2023, 2024 and 2025 in forms such as metro lines, road networks, schematic walkways, train movement and communication links. 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 Nodes/edges, path constraints, shortest/possible routes, connectivity, direction, and movement schedule, degree/count logic. Before calculation, compress the story into the smallest useful structure—a grid, table, timeline, graph or cases.

A practical solving sequence

Convert narrative to graph; label nodes and edges; mark one-way/conditional links; use path length/connectivity invariants; separate route structure from timing calculations.

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?

Good when graph is small and constraints reduce paths; risky when many conditional edges interact with time/order rules.

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

• Counting same undirected edge twice
• ignoring direction
• revisiting nodes when prohibited
• mixing route possibility with shortest route

Original practice seed

Five stations connected by directed routes with travel constraints; determine feasible itineraries and minimum transfers. 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 turn text into a graph quickly and enumerate paths systematically without duplication.

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.