Uncertain and Variable Seating

Some seating sets refuse to hand you the number of people or the exact positions, and instead say things like 'not necessarily in the same order' or 'at least three people sit between them'. These uncertain sets scare candidates, but they follow a clear method: list the possible cases, then let the clues delete the impossible ones. In SBI Clerk this variety turns up as a tougher seating block, and knowing how to handle 'not fixed' language is what separates a full set from a blank.

Reading 'Not Fixed' Language

Watch the exact wording, because it defines how much freedom you have. 'Exactly three between A and B' is rigid and fixes a gap, but 'at least three between A and B' allows several positions and must be kept open as a range. Phrases like 'not necessarily in the same order' warn that a listed sequence is not the seating order, so never place names in the order they are mentioned. Translating each vague phrase into 'fixed', 'ranged', or 'unknown' before you draw is the first discipline of these sets.

The Casework Method

When one clue can be satisfied two or three ways, open a separate small diagram for each way and carry them forward together. Label them Case 1 and Case 2, apply the next clue to both, and cross out any case that hits a contradiction. Usually all but one case dies, and even when two survive, the questions are often answerable from what the surviving cases share. Never force a single diagram when a clue genuinely branches; the branch you skipped is where the trap hides.

Persons with n between them occupy positions p and p+n+1 (n fixed = one gap; n = 'at least' -> a range)

Solved Example

Example: In a row, exactly two people sit between M and N, and M is somewhere left of N. If the row has six seats, M-N can be (1,4), (2,5) or (3,6) — three cases. Add 'M is not at an end' and you delete (1,4), leaving (2,5) and (3,6). One more clue, say 'N is 5th from left', pins it to (2,5), collapsing every case to one.

✗ Assuming 'at least two between them' means exactly two and fixing one gap  |  ✓ Keeping 'at least two' as a range of cases until another clue narrows it

Unknown Number of People

A harder twist gives no total at all, asking something like 'how many people are in the row' from position clues alone. Handle it by combining a 'from left' and a 'from right' count for the same person: if X is fourth from the left and third from the right, the total is 4 + 3 - 1 = 6, subtracting one because X is counted in both. When two people's overlapping counts are given, the minimum total assumes they overlap and the maximum assumes they do not, so such questions often ask for the least or greatest possible number. Lay out the counts on a dash line and test the overlap rather than guessing. These no-total sets look intimidating but reduce to one addition once you spot which two counts to combine, and they reward the candidate who reads the exact phrasing instead of assuming a fixed arrangement.