Seating arrangement and puzzles for RRB Group D

A seating question gives you a handful of people and a handful of clues, and exactly one arrangement fits them all. Your job is to find it, then answer one to three questions from it. Matching puzzles work the same way, except that people are matched to colours, days or jobs instead of seats.

These are the slowest questions in the reasoning section, often a minute or more each. They are still worth doing, because one correct diagram answers every question in the set. The trick is to use the clues in the same order every time.

Left and right: the one rule to get right

Most questions use a row facing north or a circle facing the centre.

The method

1. Draw the row or circle and number the seats (a row from the left).
2. Fixed clues first: "B is at the right end", "D is third from the left". These place a person for certain.
3. Next-to clues: "A is immediately left of D". Use them only once one of the two people is placed.
4. Case splits: if a clue allows two places ("J is at one of the ends"), draw both cases side by side.
5. Negative clues last: "F is not at an end". These usually settle the last seats or kill one case.
6. Check every clue against your final picture before you answer.

Worked example 1: a row

Six people, A, B, C, D, E and F, sit in a row facing north.

• B is at the right end.
• D is third from the left.
• A sits immediately to the left of D.
• C sits immediately to the right of D.
• F is not at an end.

Solving: number the seats 1–6 from the left. The fixed clues give B = 6 and D = 3. Then A = 2 and C = 4. Seats 1 and 5 remain. F is not at an end, so F = 5 and E = 1.

Row (left to right): E, A, D, C, F, B.

• At the left end: E. Between C and B: F. To the right of D: 3 people (C, F, B).

Worked example 2: a circle

Five people, P, Q, R, S and T, sit around a round table facing the centre.

• Q is immediately to the right of P.
• R is second to the left of P.
• T does not sit next to P.

Solving: number the seats 1–5 clockwise and put P in seat 1. Right is anticlockwise, so Q = seat 5. Left is clockwise, so R = seat 3. Seats 2 and 4 remain. P's neighbours are seats 2 and 5, so T cannot be in seat 2. T = 4 and S = 2.

Clockwise from P: P, S, R, T, Q.

• Between R and Q: T. Immediately to the left of P: S.

Worked example 3: a case split

Five people, J, K, L, M and N, sit in a row facing north.

• L sits in the middle.
• K sits immediately to the right of L.
• J sits at one of the ends.
• M is not at an end.
• N does not sit next to K.

Solving: L = 3 and K = 4. J is at an end, so there are two cases.

M is not at an end, so M takes seat 2 in both cases, and N gets the last seat. In case 1, N sits next to K, which breaks the last clue. So case 2 is the answer: N, M, L, K, J.

Worked example 4: a matching puzzle

Four people, P, Q, R and S, each attend a training session on a different day from Monday to Thursday.

• Q attends on Wednesday.
• P attends on an earlier day than R.
• R does not attend on Thursday.

Solving: draw a small grid of people against days. Monday, Tuesday and Thursday remain for P, R and S. R is not on Thursday, so R is on Monday or Tuesday. P must come before R, so R cannot be on Monday. R = Tuesday and P = Monday, which leaves Thursday for S.

Common mistakes

• Using the row rule for a circle. In a circle facing the centre, left is clockwise.
• Placing people from next-to clues before anyone is fixed, and then having to rub everything out.
• Dropping a case too early. Keep both cases until a clue actually breaks one.
• "Second to the left" means skip one seat, not the seat next door.

Practice set

Questions 1 to 3 use worked example 1, and question 4 uses worked example 2. For questions 5 to 8, solve this new puzzle first:

Six people, A, B, C, D, E and F, sit around a round table facing the centre. A sits opposite D. B sits immediately to the right of A. C sits second to the right of D. E does not sit next to C.

1. In example 1, who sits immediately to the right of A?
2. In example 1, how many people sit between E and C?
3. In example 1, who sits second to the left of B?
4. In example 2, who sits immediately to the right of R?
5. Who sits opposite B?
6. Who sits immediately to the left of D?
7. Who sits between C and D?
8. Who sits second to the left of B?

Answers:

1. D.
2. Two (A and D).
3. C. B is in seat 6, and two seats to the left is seat 4.
4. S. One seat anticlockwise from R.
5. F. Seats 1–6 clockwise, A in seat 1. D (opposite) = 4. B (A's right, anticlockwise) = 6. C (second to D's right) = 2. Seat 3 is next to C, so E = 5 and F = 3. Clockwise from A: A, C, F, D, E, B. Seat 3 is opposite B's seat 6.
6. E. Left is clockwise, so the seat after D (seat 5).
7. F.
8. C. Two seats clockwise from seat 6 is seat 2.

What to do next

• Draw the left–right table once from memory, especially the circle row.
• Solve two row puzzles and two circle puzzles a day for a week, using the six-step method every time.
• Revise ranking and order, and see the reasoning plan for where puzzles fit in your section time.