Question 1
Two parallel rows of chairs. Row 1 has E, B, A, D and C facing South.
Row 2 has T, P, Q, R and S facing North. Each person in one row faces exactly one person from the other row.
A sits fourth from the left end of Row 1. T faces A.
E sits at an extreme end of Row 1. B sits second to the right of E.
P sits second to the left of T. Q sits at an extreme end of Row 2.
S is not adjacent to T in Row 2.
Who faces B?
Solution Approach:
Step 1: Draw the double row setup
Row 1 faces South (↓), Row 2 faces North (↑)
Person at position i in Row 1 faces person at position i in Row 2.
Position: 1 2 3 4 5
Row 1 (↓): _ _ _ _ _
Row 2 (↑): _ _ _ _ _
Key direction rule:
- Row 1 (South-facing): "right" = viewer's LEFT (lower position numbers)
- Row 2 (North-facing): "right" = viewer's RIGHT (higher position numbers)
Step 2: Place Row 1 persons
- A sits 4th from the left end of Row 1 → Row 1, pos 4
- E sits at an extreme end: pos 1 or pos 5
- B sits second to the RIGHT of E (south-facing → lower position):
pos[B] = pos[E] - 2
If E at pos 1 → pos[B] = -1 (invalid ✗)
If E at pos 5 → pos[B] = 3 ✓ (pos 3 is free)
∴ E at pos 5, B at pos 3 ✓
Row 1: _ _ B A E
Remaining D,C at pos 1 and 2 (either order — pinned next).
Step 3: Place Row 2 persons
- T faces A (pos 4) → T at Row 2, pos 4
- P sits second to the LEFT of T (north-facing → lower position):
pos[P] = pos[T] - 2 = 2 → P at Row 2 pos 2 ✓
- Q sits at extreme end of Row 2: pos 1 or pos 5
- S is NOT adjacent to T (pos 4): adjacent = pos 3 and pos 5
So S ≠ pos 3 and S ≠ pos 5
Remaining positions for Q,R,S: pos 1, pos 3, pos 5
S not at pos 3 or pos 5 → S at pos 1
Q at extreme → pos 5 (since pos 1 is S) ✓
R fills pos 3 ✓
Row 2: S P R T Q
Final Arrangement:
Position: 1 2 3 4 5
Row 1 (↓): D/C D/C B A E
Row 2 (↑): S P R T Q
Find who faces B:
B is at Row 1, position 3.
Person at Row 2, position 3 = R
Answer: R faces B.
Step 1: Draw the double row setup
Row 1 faces South (↓), Row 2 faces North (↑)
Person at position i in Row 1 faces person at position i in Row 2.
Position: 1 2 3 4 5
Row 1 (↓): _ _ _ _ _
Row 2 (↑): _ _ _ _ _
Key direction rule:
- Row 1 (South-facing): "right" = viewer's LEFT (lower position numbers)
- Row 2 (North-facing): "right" = viewer's RIGHT (higher position numbers)
Step 2: Place Row 1 persons
- A sits 4th from the left end of Row 1 → Row 1, pos 4
- E sits at an extreme end: pos 1 or pos 5
- B sits second to the RIGHT of E (south-facing → lower position):
pos[B] = pos[E] - 2
If E at pos 1 → pos[B] = -1 (invalid ✗)
If E at pos 5 → pos[B] = 3 ✓ (pos 3 is free)
∴ E at pos 5, B at pos 3 ✓
Row 1: _ _ B A E
Remaining D,C at pos 1 and 2 (either order — pinned next).
Step 3: Place Row 2 persons
- T faces A (pos 4) → T at Row 2, pos 4
- P sits second to the LEFT of T (north-facing → lower position):
pos[P] = pos[T] - 2 = 2 → P at Row 2 pos 2 ✓
- Q sits at extreme end of Row 2: pos 1 or pos 5
- S is NOT adjacent to T (pos 4): adjacent = pos 3 and pos 5
So S ≠ pos 3 and S ≠ pos 5
Remaining positions for Q,R,S: pos 1, pos 3, pos 5
S not at pos 3 or pos 5 → S at pos 1
Q at extreme → pos 5 (since pos 1 is S) ✓
R fills pos 3 ✓
Row 2: S P R T Q
Final Arrangement:
Position: 1 2 3 4 5
Row 1 (↓): D/C D/C B A E
Row 2 (↑): S P R T Q
Find who faces B:
B is at Row 1, position 3.
Person at Row 2, position 3 = R
Answer: R faces B.