Seven persons P, Q, R, S, T, U and V are sitting in a row. T and U have one person in between them. V is immediate right to P. Q is immediate left to U. There is one person between S and P. S is not the neighbour of V. V and U have two persons between them. R is immediate left to P. Which person is sitting exactly in the middle of the row ?

Correct — option (4), V.

Take everyone in the row as facing the same way, with seats 1 to 7 numbered from left to right.

Step 1 — chain the "immediate" clues around P.
R is immediate left to P; V is immediate right to P.
Block: R P V

Step 2 — place S.
One person between S and P puts S two seats from P.
Two seats right of P is next to V, but S is not the neighbour of V.
So S is two seats left of P: S R P V

Step 3 — place U.
Two persons between V and U puts U three seats from V.
Three seats left of V is S's seat, so U is three seats right of V.
Row so far: S R P V _ _ U

Step 4 — fill the gaps.
Q is immediate left to U: S R P V _ Q U
T takes the remaining seat: S R P V T Q U

Step 5 — check T.
T and U have one person, Q, between them. ✓

The stretch from S to U needs all seven seats, so the row is fixed: S, R, P, V, T, Q, U. The 4th seat, the exact middle, holds V.

If the row faces the other way, left and right swap and the order reverses (U, Q, T, V, P, R, S); V is still in the middle.

The idea to remember: join the fixed-adjacency clues into a block first, then fit the block into the row.

Why the others are wrong

• (1)
  Q — Option (1) names Q, who sits in the 6th seat, immediately left of U at the end of the row.

  Q is placed by "Q is immediate left to U", and U has to sit three seats right of V. That puts Q two seats past the middle.

• (2)
  T — Option (2) names T, who sits in the 5th seat, immediately right of V.

  T is the last person placed: once S, R, P, V, Q and U are fixed, only seat 5 is left, and it satisfies "T and U have one person in between them". The middle seat is the one before it.

• (3)
  P — Option (3) names P, who sits in the 3rd seat.

  P has R on the left and V on the right. With S two seats to P's left, S takes seat 1 and R seat 2, so P is one seat short of the middle; V, on P's right, takes seat 4.

Linear-arrangement reasoning seats people in a row from clues about neighbours, gaps and ends.

"Immediate left" or "immediate right" puts two people in adjacent seats. "One person between" leaves one seat between them, so they sit two seats apart; "two persons between" puts them three seats apart.

A negative clue, such as "S is not the neighbour of V", places no one; it removes cases. Joining the adjacency clues into a block first leaves fewer cases to test.

Key facts

• The row from left to right: S, R, P, V, T, Q, U.
• "One person between" = two seats apart; "two persons between" = three seats apart.
• In a row of seven, the middle seat is the 4th from either end.
• S two seats right of P would sit next to V, which the clue "S is not the neighbour of V" rules out.
• Reversing the facing direction reverses the row's order but leaves the middle person unchanged.

Common traps

• Reading "one person between" as adjacent seats. It means one seat lies between them, so they are two seats apart.
• Placing S on P's right. That seat touches V, and S is not the neighbour of V.
• Taking the 3rd seat as the middle. In a row of seven, three people sit on each side of the 4th seat.

UnlockIAS will link similar questions from RAS Pre 2013 here once that paper is published on this site.

• practice — not a real PYQ

  Five friends A, B, C, D and E sit in a row facing north. C sits at the left end. B sits immediate right of A. E sits immediate left of A. D is not a neighbour of B. Who sits in the middle of the row ?

  • (a)A
  • (b)E
  • (c)D
  • (d)B
  Answer(2) — E A B is a block, and C holds seat 1, so A cannot take seat 2. If A took seat 3, D would sit in seat 5, next to B, which is not allowed; so A takes seat 4 and the row is C, D, E, A, B. Seat 3 holds E.

  Option (1) is in seat 4, option (3) in seat 2 and option (4) at the right end.

• practice — not a real PYQ

  Six people J, K, L, M, N and O sit in a row facing north. K is third from the left end. J sits immediate right of K. O sits at the right end. L sits immediate left of O. N is not at the left end. Who sits at the left end ?

  • (a)N
  • (b)L
  • (c)M
  • (d)J
  Answer(3) — K takes seat 3 and J seat 4; O takes seat 6 and L seat 5. M and N share seats 1 and 2, and N is not at the left end, so the row is M, N, K, J, L, O.

  Option (1) sits in seat 2, option (2) in seat 5 and option (4) in seat 4.