Linear Single Row South Facing Beginner-Intermediate Worksheet: Focus on common variations practice Linear Single Row South Facing BEGINNER INTERMEDIATE

Level up your Linear Single Row South Facing skills! You're at Worksheet 4 of 10 (33% through this series). This step-up challenge worksheet features 20 beginner-intermediate-level problems with a focus on common variations practice. Topics covered: linear single row south facing for competitive exams, how to solve linear single row south facing, linear single row south facing tricks.

📝 Worksheet 4 of 10 • 20 questions • ⏱️ Estimated time: 20 minutes • 🎯 Beginner Intermediate level

What you'll learn in this worksheet:
Your progress through Linear Single Row South Facing
Worksheet 4 of 10 (33% complete)

Question 1

Five friends P, Q, S, R and T are sitting in a row facing South. P sits at the right extreme end. Q sits second to the right of S. T sits immediately to the right of S (from viewer's perspective). R is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- Q sits second to the right of S:
South-facing right = viewer's left = lower position: pos[Q] = pos[S] - 2
Possible: S=3→Q=1, or S=4→Q=2
- T sits immediately to the right of S (viewer's right = higher pos): pos[T] = pos[S] + 1
If S=3 → T=4 ✓ (pos 4 free)
If S=4 → T=5 = P ✗ (conflict)
∴ S=3, Q=1, T=4

Position: Q _ S T P

Step 4: Apply constraint
- R not adjacent to P (pos 5): R ≠ pos 4 (taken by T) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: Q R S T P

Verification:
✓ P at right extreme end (pos 5)
✓ Q second to right of S: pos[Q](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ T immediately right of S (viewer right): pos 3+1 = 4
✓ R not adjacent to P (pos 2, not pos 4)

Answer: Q sits at the left extreme end (position 1).

Question 2

Five friends T, Q, P, R and S are sitting in a row facing South. T sits at the right extreme end. Q sits second to the right of P. S sits immediately to the right of P (from viewer's perspective). R is not adjacent to T. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- T at the right extreme end → Position 5
- Q sits second to the right of P:
South-facing right = viewer's left = lower position: pos[Q] = pos[P] - 2
Possible: P=3→Q=1, or P=4→Q=2
- S sits immediately to the right of P (viewer's right = higher pos): pos[S] = pos[P] + 1
If P=3 → S=4 ✓ (pos 4 free)
If P=4 → S=5 = T ✗ (conflict)
∴ P=3, Q=1, S=4

Position: Q _ P S T

Step 4: Apply constraint
- R not adjacent to T (pos 5): R ≠ pos 4 (taken by S) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: Q R P S T

Verification:
✓ T at right extreme end (pos 5)
✓ Q second to right of P: pos[Q](=1)-2 = 3 = pos[P] (south-facing right=lower)
✓ S immediately right of P (viewer right): pos 3+1 = 4
✓ R not adjacent to T (pos 2, not pos 4)

Answer: Q sits at the left extreme end (position 1).

Question 3

Five friends P, S, T, R and Q are sitting in a row facing South. P sits at the right extreme end. S sits second to the right of T. Q sits immediately to the right of T (from viewer's perspective). R is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- S sits second to the right of T:
South-facing right = viewer's left = lower position: pos[S] = pos[T] - 2
Possible: T=3→S=1, or T=4→S=2
- Q sits immediately to the right of T (viewer's right = higher pos): pos[Q] = pos[T] + 1
If T=3 → Q=4 ✓ (pos 4 free)
If T=4 → Q=5 = P ✗ (conflict)
∴ T=3, S=1, Q=4

Position: S _ T Q P

Step 4: Apply constraint
- R not adjacent to P (pos 5): R ≠ pos 4 (taken by Q) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: S R T Q P

Verification:
✓ P at right extreme end (pos 5)
✓ S second to right of T: pos[S](=1)-2 = 3 = pos[T] (south-facing right=lower)
✓ Q immediately right of T (viewer right): pos 3+1 = 4
✓ R not adjacent to P (pos 2, not pos 4)

Answer: S sits at the left extreme end (position 1).

Question 4

Five friends R, T, Q, P and S are sitting in a row facing South. R sits at the right extreme end. T sits second to the right of Q. S sits immediately to the right of Q (from viewer's perspective). P is not adjacent to R. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- R at the right extreme end → Position 5
- T sits second to the right of Q:
South-facing right = viewer's left = lower position: pos[T] = pos[Q] - 2
Possible: Q=3→T=1, or Q=4→T=2
- S sits immediately to the right of Q (viewer's right = higher pos): pos[S] = pos[Q] + 1
If Q=3 → S=4 ✓ (pos 4 free)
If Q=4 → S=5 = R ✗ (conflict)
∴ Q=3, T=1, S=4

Position: T _ Q S R

Step 4: Apply constraint
- P not adjacent to R (pos 5): P ≠ pos 4 (taken by S) → P at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: T P Q S R

Verification:
✓ R at right extreme end (pos 5)
✓ T second to right of Q: pos[T](=1)-2 = 3 = pos[Q] (south-facing right=lower)
✓ S immediately right of Q (viewer right): pos 3+1 = 4
✓ P not adjacent to R (pos 2, not pos 4)

Answer: T sits at the left extreme end (position 1).

Question 5

Five friends T, P, S, R and Q are sitting in a row facing South. T sits at the right extreme end. P sits second to the right of S. Q sits immediately to the right of S (from viewer's perspective). R is not adjacent to T. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- T at the right extreme end → Position 5
- P sits second to the right of S:
South-facing right = viewer's left = lower position: pos[P] = pos[S] - 2
Possible: S=3→P=1, or S=4→P=2
- Q sits immediately to the right of S (viewer's right = higher pos): pos[Q] = pos[S] + 1
If S=3 → Q=4 ✓ (pos 4 free)
If S=4 → Q=5 = T ✗ (conflict)
∴ S=3, P=1, Q=4

Position: P _ S Q T

Step 4: Apply constraint
- R not adjacent to T (pos 5): R ≠ pos 4 (taken by Q) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: P R S Q T

Verification:
✓ T at right extreme end (pos 5)
✓ P second to right of S: pos[P](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ Q immediately right of S (viewer right): pos 3+1 = 4
✓ R not adjacent to T (pos 2, not pos 4)

Answer: P sits at the left extreme end (position 1).

Question 6

Five friends Q, P, T, R and S are sitting in a row facing South. Q sits at the right extreme end. P sits second to the right of T. S sits immediately to the right of T (from viewer's perspective). R is not adjacent to Q. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- Q at the right extreme end → Position 5
- P sits second to the right of T:
South-facing right = viewer's left = lower position: pos[P] = pos[T] - 2
Possible: T=3→P=1, or T=4→P=2
- S sits immediately to the right of T (viewer's right = higher pos): pos[S] = pos[T] + 1
If T=3 → S=4 ✓ (pos 4 free)
If T=4 → S=5 = Q ✗ (conflict)
∴ T=3, P=1, S=4

Position: P _ T S Q

Step 4: Apply constraint
- R not adjacent to Q (pos 5): R ≠ pos 4 (taken by S) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: P R T S Q

Verification:
✓ Q at right extreme end (pos 5)
✓ P second to right of T: pos[P](=1)-2 = 3 = pos[T] (south-facing right=lower)
✓ S immediately right of T (viewer right): pos 3+1 = 4
✓ R not adjacent to Q (pos 2, not pos 4)

Answer: P sits at the left extreme end (position 1).

Question 7

Five friends T, S, P, Q and R are sitting in a row facing South. T sits at the right extreme end. S sits second to the right of P. R sits immediately to the right of P (from viewer's perspective). Q is not adjacent to T. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- T at the right extreme end → Position 5
- S sits second to the right of P:
South-facing right = viewer's left = lower position: pos[S] = pos[P] - 2
Possible: P=3→S=1, or P=4→S=2
- R sits immediately to the right of P (viewer's right = higher pos): pos[R] = pos[P] + 1
If P=3 → R=4 ✓ (pos 4 free)
If P=4 → R=5 = T ✗ (conflict)
∴ P=3, S=1, R=4

Position: S _ P R T

Step 4: Apply constraint
- Q not adjacent to T (pos 5): Q ≠ pos 4 (taken by R) → Q at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: S Q P R T

Verification:
✓ T at right extreme end (pos 5)
✓ S second to right of P: pos[S](=1)-2 = 3 = pos[P] (south-facing right=lower)
✓ R immediately right of P (viewer right): pos 3+1 = 4
✓ Q not adjacent to T (pos 2, not pos 4)

Answer: S sits at the left extreme end (position 1).

Question 8

Five friends P, Q, S, R and T are sitting in a row facing South. P sits at the right extreme end. Q sits second to the right of S. T sits immediately to the right of S (from viewer's perspective). R is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- Q sits second to the right of S:
South-facing right = viewer's left = lower position: pos[Q] = pos[S] - 2
Possible: S=3→Q=1, or S=4→Q=2
- T sits immediately to the right of S (viewer's right = higher pos): pos[T] = pos[S] + 1
If S=3 → T=4 ✓ (pos 4 free)
If S=4 → T=5 = P ✗ (conflict)
∴ S=3, Q=1, T=4

Position: Q _ S T P

Step 4: Apply constraint
- R not adjacent to P (pos 5): R ≠ pos 4 (taken by T) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: Q R S T P

Verification:
✓ P at right extreme end (pos 5)
✓ Q second to right of S: pos[Q](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ T immediately right of S (viewer right): pos 3+1 = 4
✓ R not adjacent to P (pos 2, not pos 4)

Answer: Q sits at the left extreme end (position 1).

Question 9

Five friends S, Q, R, T and P are sitting in a row facing South. S sits at the right extreme end. Q sits second to the right of R. P sits immediately to the right of R (from viewer's perspective). T is not adjacent to S. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- S at the right extreme end → Position 5
- Q sits second to the right of R:
South-facing right = viewer's left = lower position: pos[Q] = pos[R] - 2
Possible: R=3→Q=1, or R=4→Q=2
- P sits immediately to the right of R (viewer's right = higher pos): pos[P] = pos[R] + 1
If R=3 → P=4 ✓ (pos 4 free)
If R=4 → P=5 = S ✗ (conflict)
∴ R=3, Q=1, P=4

Position: Q _ R P S

Step 4: Apply constraint
- T not adjacent to S (pos 5): T ≠ pos 4 (taken by P) → T at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: Q T R P S

Verification:
✓ S at right extreme end (pos 5)
✓ Q second to right of R: pos[Q](=1)-2 = 3 = pos[R] (south-facing right=lower)
✓ P immediately right of R (viewer right): pos 3+1 = 4
✓ T not adjacent to S (pos 2, not pos 4)

Answer: Q sits at the left extreme end (position 1).

Question 10

Five friends R, Q, T, P and S are sitting in a row facing South. R sits at the right extreme end. Q sits second to the right of T. S sits immediately to the right of T (from viewer's perspective). P is not adjacent to R. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- R at the right extreme end → Position 5
- Q sits second to the right of T:
South-facing right = viewer's left = lower position: pos[Q] = pos[T] - 2
Possible: T=3→Q=1, or T=4→Q=2
- S sits immediately to the right of T (viewer's right = higher pos): pos[S] = pos[T] + 1
If T=3 → S=4 ✓ (pos 4 free)
If T=4 → S=5 = R ✗ (conflict)
∴ T=3, Q=1, S=4

Position: Q _ T S R

Step 4: Apply constraint
- P not adjacent to R (pos 5): P ≠ pos 4 (taken by S) → P at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: Q P T S R

Verification:
✓ R at right extreme end (pos 5)
✓ Q second to right of T: pos[Q](=1)-2 = 3 = pos[T] (south-facing right=lower)
✓ S immediately right of T (viewer right): pos 3+1 = 4
✓ P not adjacent to R (pos 2, not pos 4)

Answer: Q sits at the left extreme end (position 1).

Question 11

Five friends Q, R, S, T and P are sitting in a row facing South. Q sits at the right extreme end. R sits second to the right of S. P sits immediately to the right of S (from viewer's perspective). T is not adjacent to Q. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- Q at the right extreme end → Position 5
- R sits second to the right of S:
South-facing right = viewer's left = lower position: pos[R] = pos[S] - 2
Possible: S=3→R=1, or S=4→R=2
- P sits immediately to the right of S (viewer's right = higher pos): pos[P] = pos[S] + 1
If S=3 → P=4 ✓ (pos 4 free)
If S=4 → P=5 = Q ✗ (conflict)
∴ S=3, R=1, P=4

Position: R _ S P Q

Step 4: Apply constraint
- T not adjacent to Q (pos 5): T ≠ pos 4 (taken by P) → T at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: R T S P Q

Verification:
✓ Q at right extreme end (pos 5)
✓ R second to right of S: pos[R](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ P immediately right of S (viewer right): pos 3+1 = 4
✓ T not adjacent to Q (pos 2, not pos 4)

Answer: R sits at the left extreme end (position 1).

Question 12

Five friends R, P, S, Q and T are sitting in a row facing South. R sits at the right extreme end. P sits second to the right of S. T sits immediately to the right of S (from viewer's perspective). Q is not adjacent to R. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- R at the right extreme end → Position 5
- P sits second to the right of S:
South-facing right = viewer's left = lower position: pos[P] = pos[S] - 2
Possible: S=3→P=1, or S=4→P=2
- T sits immediately to the right of S (viewer's right = higher pos): pos[T] = pos[S] + 1
If S=3 → T=4 ✓ (pos 4 free)
If S=4 → T=5 = R ✗ (conflict)
∴ S=3, P=1, T=4

Position: P _ S T R

Step 4: Apply constraint
- Q not adjacent to R (pos 5): Q ≠ pos 4 (taken by T) → Q at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: P Q S T R

Verification:
✓ R at right extreme end (pos 5)
✓ P second to right of S: pos[P](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ T immediately right of S (viewer right): pos 3+1 = 4
✓ Q not adjacent to R (pos 2, not pos 4)

Answer: P sits at the left extreme end (position 1).

Question 13

Five friends T, S, Q, R and P are sitting in a row facing South. T sits at the right extreme end. S sits second to the right of Q. P sits immediately to the right of Q (from viewer's perspective). R is not adjacent to T. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- T at the right extreme end → Position 5
- S sits second to the right of Q:
South-facing right = viewer's left = lower position: pos[S] = pos[Q] - 2
Possible: Q=3→S=1, or Q=4→S=2
- P sits immediately to the right of Q (viewer's right = higher pos): pos[P] = pos[Q] + 1
If Q=3 → P=4 ✓ (pos 4 free)
If Q=4 → P=5 = T ✗ (conflict)
∴ Q=3, S=1, P=4

Position: S _ Q P T

Step 4: Apply constraint
- R not adjacent to T (pos 5): R ≠ pos 4 (taken by P) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: S R Q P T

Verification:
✓ T at right extreme end (pos 5)
✓ S second to right of Q: pos[S](=1)-2 = 3 = pos[Q] (south-facing right=lower)
✓ P immediately right of Q (viewer right): pos 3+1 = 4
✓ R not adjacent to T (pos 2, not pos 4)

Answer: S sits at the left extreme end (position 1).

Question 14

Five friends Q, R, S, T and P are sitting in a row facing South. Q sits at the right extreme end. R sits second to the right of S. P sits immediately to the right of S (from viewer's perspective). T is not adjacent to Q. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- Q at the right extreme end → Position 5
- R sits second to the right of S:
South-facing right = viewer's left = lower position: pos[R] = pos[S] - 2
Possible: S=3→R=1, or S=4→R=2
- P sits immediately to the right of S (viewer's right = higher pos): pos[P] = pos[S] + 1
If S=3 → P=4 ✓ (pos 4 free)
If S=4 → P=5 = Q ✗ (conflict)
∴ S=3, R=1, P=4

Position: R _ S P Q

Step 4: Apply constraint
- T not adjacent to Q (pos 5): T ≠ pos 4 (taken by P) → T at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: R T S P Q

Verification:
✓ Q at right extreme end (pos 5)
✓ R second to right of S: pos[R](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ P immediately right of S (viewer right): pos 3+1 = 4
✓ T not adjacent to Q (pos 2, not pos 4)

Answer: R sits at the left extreme end (position 1).

Question 15

Five friends P, T, R, Q and S are sitting in a row facing South. P sits at the right extreme end. T sits second to the right of R. S sits immediately to the right of R (from viewer's perspective). Q is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- T sits second to the right of R:
South-facing right = viewer's left = lower position: pos[T] = pos[R] - 2
Possible: R=3→T=1, or R=4→T=2
- S sits immediately to the right of R (viewer's right = higher pos): pos[S] = pos[R] + 1
If R=3 → S=4 ✓ (pos 4 free)
If R=4 → S=5 = P ✗ (conflict)
∴ R=3, T=1, S=4

Position: T _ R S P

Step 4: Apply constraint
- Q not adjacent to P (pos 5): Q ≠ pos 4 (taken by S) → Q at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: T Q R S P

Verification:
✓ P at right extreme end (pos 5)
✓ T second to right of R: pos[T](=1)-2 = 3 = pos[R] (south-facing right=lower)
✓ S immediately right of R (viewer right): pos 3+1 = 4
✓ Q not adjacent to P (pos 2, not pos 4)

Answer: T sits at the left extreme end (position 1).

Question 16

Five friends R, P, S, T and Q are sitting in a row facing South. R sits at the right extreme end. P sits second to the right of S. Q sits immediately to the right of S (from viewer's perspective). T is not adjacent to R. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- R at the right extreme end → Position 5
- P sits second to the right of S:
South-facing right = viewer's left = lower position: pos[P] = pos[S] - 2
Possible: S=3→P=1, or S=4→P=2
- Q sits immediately to the right of S (viewer's right = higher pos): pos[Q] = pos[S] + 1
If S=3 → Q=4 ✓ (pos 4 free)
If S=4 → Q=5 = R ✗ (conflict)
∴ S=3, P=1, Q=4

Position: P _ S Q R

Step 4: Apply constraint
- T not adjacent to R (pos 5): T ≠ pos 4 (taken by Q) → T at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: P T S Q R

Verification:
✓ R at right extreme end (pos 5)
✓ P second to right of S: pos[P](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ Q immediately right of S (viewer right): pos 3+1 = 4
✓ T not adjacent to R (pos 2, not pos 4)

Answer: P sits at the left extreme end (position 1).

Question 17

Five friends P, S, T, R and Q are sitting in a row facing South. P sits at the right extreme end. S sits second to the right of T. Q sits immediately to the right of T (from viewer's perspective). R is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- S sits second to the right of T:
South-facing right = viewer's left = lower position: pos[S] = pos[T] - 2
Possible: T=3→S=1, or T=4→S=2
- Q sits immediately to the right of T (viewer's right = higher pos): pos[Q] = pos[T] + 1
If T=3 → Q=4 ✓ (pos 4 free)
If T=4 → Q=5 = P ✗ (conflict)
∴ T=3, S=1, Q=4

Position: S _ T Q P

Step 4: Apply constraint
- R not adjacent to P (pos 5): R ≠ pos 4 (taken by Q) → R at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: S R T Q P

Verification:
✓ P at right extreme end (pos 5)
✓ S second to right of T: pos[S](=1)-2 = 3 = pos[T] (south-facing right=lower)
✓ Q immediately right of T (viewer right): pos 3+1 = 4
✓ R not adjacent to P (pos 2, not pos 4)

Answer: S sits at the left extreme end (position 1).

Question 18

Five friends Q, P, S, T and R are sitting in a row facing South. Q sits at the right extreme end. P sits second to the right of S. R sits immediately to the right of S (from viewer's perspective). T is not adjacent to Q. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- Q at the right extreme end → Position 5
- P sits second to the right of S:
South-facing right = viewer's left = lower position: pos[P] = pos[S] - 2
Possible: S=3→P=1, or S=4→P=2
- R sits immediately to the right of S (viewer's right = higher pos): pos[R] = pos[S] + 1
If S=3 → R=4 ✓ (pos 4 free)
If S=4 → R=5 = Q ✗ (conflict)
∴ S=3, P=1, R=4

Position: P _ S R Q

Step 4: Apply constraint
- T not adjacent to Q (pos 5): T ≠ pos 4 (taken by R) → T at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: P T S R Q

Verification:
✓ Q at right extreme end (pos 5)
✓ P second to right of S: pos[P](=1)-2 = 3 = pos[S] (south-facing right=lower)
✓ R immediately right of S (viewer right): pos 3+1 = 4
✓ T not adjacent to Q (pos 2, not pos 4)

Answer: P sits at the left extreme end (position 1).

Question 19

Five friends R, S, T, P and Q are sitting in a row facing South. R sits at the right extreme end. S sits second to the right of T. Q sits immediately to the right of T (from viewer's perspective). P is not adjacent to R. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- R at the right extreme end → Position 5
- S sits second to the right of T:
South-facing right = viewer's left = lower position: pos[S] = pos[T] - 2
Possible: T=3→S=1, or T=4→S=2
- Q sits immediately to the right of T (viewer's right = higher pos): pos[Q] = pos[T] + 1
If T=3 → Q=4 ✓ (pos 4 free)
If T=4 → Q=5 = R ✗ (conflict)
∴ T=3, S=1, Q=4

Position: S _ T Q R

Step 4: Apply constraint
- P not adjacent to R (pos 5): P ≠ pos 4 (taken by Q) → P at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: S P T Q R

Verification:
✓ R at right extreme end (pos 5)
✓ S second to right of T: pos[S](=1)-2 = 3 = pos[T] (south-facing right=lower)
✓ Q immediately right of T (viewer right): pos 3+1 = 4
✓ P not adjacent to R (pos 2, not pos 4)

Answer: S sits at the left extreme end (position 1).

Question 20

Five friends P, T, R, S and Q are sitting in a row facing South. P sits at the right extreme end. T sits second to the right of R. Q sits immediately to the right of R (from viewer's perspective). S is not adjacent to P. Who sits at the left extreme end?
Solution Approach:

Step 1: Understanding facing South
When persons face South:
- Their right hand points West (viewer's LEFT) — "right" in the question = lower position number
- Viewer's "right" (higher position) = person's left side

Step 2: Set up diagram (viewer's perspective)
Position: 1(left) 2 3 4 5(right)

Step 3: Apply conditions
- P at the right extreme end → Position 5
- T sits second to the right of R:
South-facing right = viewer's left = lower position: pos[T] = pos[R] - 2
Possible: R=3→T=1, or R=4→T=2
- Q sits immediately to the right of R (viewer's right = higher pos): pos[Q] = pos[R] + 1
If R=3 → Q=4 ✓ (pos 4 free)
If R=4 → Q=5 = P ✗ (conflict)
∴ R=3, T=1, Q=4

Position: T _ R Q P

Step 4: Apply constraint
- S not adjacent to P (pos 5): S ≠ pos 4 (taken by Q) → S at pos 2 ✓

Final Arrangement (all facing South ↓):
Position: T S R Q P

Verification:
✓ P at right extreme end (pos 5)
✓ T second to right of R: pos[T](=1)-2 = 3 = pos[R] (south-facing right=lower)
✓ Q immediately right of R (viewer right): pos 3+1 = 4
✓ S not adjacent to P (pos 2, not pos 4)

Answer: T sits at the left extreme end (position 1).
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