Ordering Deduction

When two clues both say someone is to the right of two other people, that person must be the rightmost of the three. Draw a simple left-to-right number line, place the person the clues point to on the far right, and see which answer statement is always true.

Two-clue three-person ordering questions (find who must be true) appear in the very easy band of OC TS. They are near-certain marks for students who draw a quick diagram rather than reasoning in their head.

The examiner checks whether students can combine two “A is right of B” constraints and correctly deduce that A must be the rightmost person — and recognise that the relative order of the other two remains unknown.

Three people stand in a row. Two clues each say Person A is to the right of one of the others. Students must find which of four statements — including “A is in the middle” and “A is furthest right” — must be true.

This is a great starting point for ordering problems: three clues, five teams, one winner to find. The secret is to always start with the clue that gives you a fixed position — once you anchor Yellow at 3rd, the other positions fall into place very quickly.

Three-clue chain ordering questions appear regularly in the easy range of OC TS and reward students who work through the clues in the right order rather than trying to hold everything in their head at once.

The examiner wants to see whether you can build a position chain from relative clues — "after Red but before Yellow" compresses three positions into one locked sequence. Students who try to guess from the options rather than building the chain often confuse 1st and 2nd.

Five teams or people compete in a race or ordering task. One clue fixes a position (e.g. "Yellow finished third"). A chain clue ties two others around that anchor (e.g. "Green after Red but before Yellow"). A final clue places the remaining two relative to the anchor. You must identify who came first.

Peter has a book for Fiona but cannot see her today. He gives it to Zhang at 09:00. Meanwhile Sam→Tim at 10:00, Tim→Ursula at 11:00, Ursula→Fiona at 12:00. The right-hand chain is complete — but Zhang is isolated. The missing link is a meeting that connects Zhang into the chain before the chain moves on without the book.

Short 4–5 person relay questions with one obvious missing link appear regularly in the easier half of OC TS chain questions. The trap options always involve the right people but wrong timing (too early, too late, or the person doesn't have the object yet). Checking timing order is as important as checking who meets whom.

The examiner tests whether students can identify a gap in a relay chain (Zhang has the book but is disconnected from the Tim→Ursula→Fiona chain) and select the extra meeting that correctly bridges the gap with valid timing. Trap D (Zhang→Ursula at 12:30) is designed to catch students who ignore the timing — Ursula already met Fiona at 12:00.

An object (book, card, package) must travel from Person A to Person Z. Several meetings are scheduled but one link in the chain is absent. One extra meeting is needed to bridge the gap. Trap options include: meetings with wrong timing (too late or before the object arrives), meetings involving people outside the main chain, and meetings between the right people but where neither person has the object yet.

Relay Logic questions are one of the most practically engaging types in Ordering Deduction — an object must travel from one person to another through a chain of timed handovers, and your job is to find where the chain breaks and what single extra meeting would repair it. The approach is always the same: trace forward from where the object starts.

Chain of handovers questions appear regularly in the medium difficulty range of OC TS and reward students who think in chains rather than individually about each meeting. The most common mistake is picking a meeting that involves the right people but at a time before the object could have reached them.

The examiner wants to confirm that you can map a relay chain, identify exactly which link is missing, and verify that the proposed fix happens at the right time — after the object arrives with the sender AND before the recipient needs to pass it on.

An object must be delivered from Person A to Person Z via a sequence of handovers. Several meetings are listed, but one crucial link is absent — a meeting between the person currently holding the object and the person who needs to pass it next. You pick which extra meeting would complete the chain.

Ordering problems do not always come as a list of finish positions. This one involves heights and stairs — and the key insight is that a staircase works like a measuring scale in reverse: taller people go on lower steps, shorter people go on higher steps, so everyone's head reaches the same level. Once you see that, the "impossible" option stands out immediately.

Height-compensation spatial ordering questions appear occasionally in OC TS and reward students who can translate a physical situation into a height ranking. The most common mistake is forgetting that the problem is underdetermined (we don't know Izzy vs Melissa) and wrongly ruling out options that are valid in one of the two possible scenarios.

The examiner is testing two skills at once: correctly ranking heights from relative clues (knowing that Caitlin is shortest, but that Izzy vs Melissa is unknown), and applying a staircase logic rule (shorter person → higher step) to determine which step assignments are forced and which are flexible.

Two or three clues establish a partial height order. A compensating physical setup (stairs, boxes, platforms) means each person's final head position depends on their natural height plus their step elevation. You must find the one step assignment that contradicts the forced height rank.

Idris has four treasure boxes (W, X, Y, Z) and three ordering clues. From them he can work out W > X > Z and W > Y — but Y's position relative to X and Z is still unknown (three possibilities). The question asks which fourth clue would make the ordering unique. The trick is to test each option and see whether it collapses all possibilities to exactly one.

'Find the completing clue' ordering questions appear occasionally in OC TS as a harder variant of standard linear ordering. They reward students who think systematically about gaps — what is not yet determined — rather than just what is already known. The most common mistake is picking option D (Y > Z), which narrows to two possibilities instead of one.

The examiner is testing whether students can identify what is already determined (W > X > Z, W > Y) and what remains undetermined (Y's position relative to X and Z), then find the single extra clue that resolves that ambiguity completely. Students who only check that an option is 'consistent' with the clues will incorrectly select B, C, or D.

Four items must be placed in a strict unique order. Three ordering clues are given. From them, a partial order is established but one item (Y) has multiple valid positions. Four options each propose a different fourth clue. Only one option, combined with the existing three clues, forces a unique complete ordering. The others either leave two orderings open or add a clue already implied by the existing set.

Five-person ordering puzzles are the flagship challenge of this unit — and they are far more systematic than they look. With five people and five clues, your brain wants to try every combination. But the right method cuts through all of that: anchor the one fixed position first, use chain clues to compress the remaining space, and treat adjacency pairs as locked units.

Five-person ordering questions with mixed relative, adjacency, and exclusion clues appear consistently in the difficult half of OC TS. They reward students who have a practised approach over those who rely on intuition. The same four clue types recur in almost every version: "last/first", "A before B", "immediately before", and "not first".

The examiner is testing whether you can simultaneously satisfy multiple ordering constraints — a fixed position anchor, a relative ordering chain, an adjacency constraint, and a position exclusion — and find the unique arrangement that satisfies all of them without contradiction.

Five people must be placed in positions 1–5. You get: one fixed-position clue (e.g. "Quinn is last"), one or two relative ordering chains (e.g. "Sasha before Ravi before Quinn"), one adjacency clue (e.g. "Tia immediately before Priya"), and one exclusion clue (e.g. "Tia is not first"). You are asked who occupies a specific position.