Question 1
There are 10 seats in a row, all facing North. 8 persons D, E, B, C, A, G, F and H are seated, leaving 2 seats empty.
D sits at seat 3. H sits at seat 8.
One empty seat is at an extreme end. E sits immediately to the right of an empty seat.
C sits fourth to the left of H.
How many persons sit between the two empty seats?
Solution Approach:
Step 1: Mark total positions
Seats: 1 2 3 4 5 6 7 8 9 10
Total: 10 seats, 8 persons, 2 empty.
Step 2: Place definite positions
- D at seat 3
- H at seat 8 (seat 8)
- One empty seat at extreme end → seat 1 is empty
Seat: 1(_) 2(_) 3(D) 4(_) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 3: Apply empty seat adjacency
- E sits immediately to the RIGHT of an empty seat
- Empty at seat 1 → seat 2 = E ✓
Seat: 1(_) 2(E) 3(D) 4(_) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 4: Apply "fourth to the left" condition
- C sits fourth to the LEFT of H (seat 8)
- Fourth to left: 8 → 7 → 6 → 5 → 4
- C at seat 4 ✓
Seat: 1(_) 2(E) 3(D) 4(C) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 5: Locate second empty seat
Remaining persons: A, G, F, B → fill seats 5, 6, 7, 9, 10 minus one empty.
After placing A(5), G(6), F(7), B(10): seat 9 is empty.
Step 6: Final arrangement
Seat: 1(_) 2(E) 3(D) 4(C) 5(A) 6(G) 7(F) 8(H) 9(_) 10(B)
Count persons between empty seats (seat 1 and seat 9):
Seats 2 through 8: E, D, C, A, G, F, H = 7 persons
Verification:
✓ D at seat 3
✓ H at seat 8
✓ Empty at seat 1 (extreme end)
✓ E immediately right of empty seat 1
✓ C fourth to left of H (seat 4 = seat 8 - 4)
Answer: 7 persons sit between the two empty seats.
Step 1: Mark total positions
Seats: 1 2 3 4 5 6 7 8 9 10
Total: 10 seats, 8 persons, 2 empty.
Step 2: Place definite positions
- D at seat 3
- H at seat 8 (seat 8)
- One empty seat at extreme end → seat 1 is empty
Seat: 1(_) 2(_) 3(D) 4(_) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 3: Apply empty seat adjacency
- E sits immediately to the RIGHT of an empty seat
- Empty at seat 1 → seat 2 = E ✓
Seat: 1(_) 2(E) 3(D) 4(_) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 4: Apply "fourth to the left" condition
- C sits fourth to the LEFT of H (seat 8)
- Fourth to left: 8 → 7 → 6 → 5 → 4
- C at seat 4 ✓
Seat: 1(_) 2(E) 3(D) 4(C) 5(_) 6(_) 7(_) 8(H) 9(_) 10(_)
Step 5: Locate second empty seat
Remaining persons: A, G, F, B → fill seats 5, 6, 7, 9, 10 minus one empty.
After placing A(5), G(6), F(7), B(10): seat 9 is empty.
Step 6: Final arrangement
Seat: 1(_) 2(E) 3(D) 4(C) 5(A) 6(G) 7(F) 8(H) 9(_) 10(B)
Count persons between empty seats (seat 1 and seat 9):
Seats 2 through 8: E, D, C, A, G, F, H = 7 persons
Verification:
✓ D at seat 3
✓ H at seat 8
✓ Empty at seat 1 (extreme end)
✓ E immediately right of empty seat 1
✓ C fourth to left of H (seat 4 = seat 8 - 4)
Answer: 7 persons sit between the two empty seats.