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Question

Seven friends S1, S2, S3, S4, S5, S6 and S7 are sitting in a row facing towards north (not necessarily in the same order). S4 does not sit at any of the extreme ends. Only three friends sit between S5 and S7. Only two friends sit between S3 and S5. Both S5 and S7 do not sit at any of the extreme ends. S2 sits in the middle of the row.
Who are the neighbours of S2?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
S4 and S3

Step 1: Determine the Middle Position

Seven friends are sitting in a row. The middle position in a row of 7 is the 4th position. S2 is located at this position.

Arrangement: $_ _ _ S2 _ _ _$

Step 2: Locate S5 and S7

There are 3 friends between S5 and S7. This implies their positions could be {1, 5}, {2, 6}, or {3, 7}.

Both S5 and S7 are not at the extreme ends (positions 1 and 7).

Combining these conditions, the only possible positions for S5 and S7 are 2 and 6.

Step 3: Determine S3's Position

There are 2 friends between S3 and S5.

Case A: If S5 is at position 2.

  • The arrangement is $_ S5 _ S2 _ S7 _$.
  • To place 2 friends between S3 and S5(2), S3 must be at position 5. (Friends at positions 3 and 4).
  • Partial arrangement: $_ S5 _ S2 S3 S7 _$

Case B: If S5 is at position 6.

  • The arrangement is $_ S7 _ S2 _ S5 _$.
  • To place 2 friends between S3 and S5(6), S3 must be at position 3. (Friends at positions 4 and 5).
  • Partial arrangement: $_ S7 S3 S2 _ S5 _$

Step 4: Place S4 and Finalize Arrangement

S4 is not at any extreme end (positions 1 and 7).

Consider Case A (S5 at 2, S3 at 5, S7 at 6):

  • Arrangement: $_ S5 _ S2 S3 S7 _$
  • Remaining positions: 1, 3, 7. Remaining friends: S1, S4, S6.
  • Since S4 cannot be at ends 1 or 7, S4 must be at position 3.
  • Final arrangement: $S1/S6 S5 S4 S2 S3 S7 S1/S6$
  • The neighbors of S2 (at position 4) are the individuals at positions 3 and 5, which are S4 and S3.

Consider Case B (S7 at 2, S3 at 3, S5 at 6):

  • Arrangement: $_ S7 S3 S2 _ S5 _$
  • Remaining positions: 1, 5, 7. Remaining friends: S1, S4, S6.
  • Since S4 cannot be at ends 1 or 7, S4 must be at position 5.
  • Final arrangement: $S1/S6 S7 S3 S2 S4 S5 S1/S6$
  • The neighbors of S2 (at position 4) are the individuals at positions 3 and 5, which are S3 and S4.

Step 5: Identify Neighbors of S2

Both valid seating arrangements consistently show that S3 and S4 are the immediate neighbors of S2.

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Similar Questions

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  10. Study the given information carefully and answer the question that follows.

    Eight persons A, B, C, D, E, F, G and H are sitting in a row facing the north but not necessarily in the same order. Three persons are sitting between D and F. G is sitting to the immediate left of D. Only one person is sitting between E and B. E is not sitting at any of the extreme ends. More than three persons are sitting between H and A. A is sitting to the left of H. Either H or A is sitting at one of the ends. Neither D nor F is sitting at any of the extreme ends. E and B are not the immediate neighbours of G and D. E is sitting to the right of B.

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Important Questions from Linear Arrangement

  1. M, N, L, O, Q and H are sitting in a row. Q and H are in the centre. M and N are at the ends. L is sitting to the immediate left of N. Who is to the right of M?

  2. Five friends, Shruti, Shreya, Anup, Ankit and Kiran, are sitting in a row facing towards the south. Shruti is between Shreya and Anup. Kiran and Shreya are sitting at the extreme ends of the west and east, respectively. Who is sitting in the middle?

  3. Five students are standing in a line. Suman is standing next to Pranav but not next to Deena. Kumar is standing next to Raju, who is standing on the extreme left, and Deena is not standing next to Kumar.

    Who is standing in the middle?
  4. Eight friends, A, B, C, D, E, F, G and H, are sitting in a straight line, all facing the north. F is sitting between D and G. B is sitting between H and A. E is third to the left of G. G is sitting at one of the corners. H is third to the left of C. Who is sitting between A and E?

  5. Five students are sitting in a row. Akbar is to the left of the person sitting in the middle, but to the right of Sekar. Prakash is to the right of Deva, and Ram is to the right of Prakash. Ram is second from the person sitting in the middle. Who is the person sitting in the middle?

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