Six persons are seated in a row facing north. Each has a different age, but their order is unknown. Given the following clues:

- C sits 3rd from one end.
- The person who is 12 years old sits 2nd to the right of C.
- The number of persons to the right of the 12-year-old is equal to the number of persons to the left of D.
- O sits 2nd to the right of the person who is 6 years old.
- Two persons sit between D and B, and B's age is twice that of D.
- N sits to the right of P.
- The person who is 36 years old sits 3rd to the left of the person who is 15 years old.
- O is 18 years old.

**Question:** Who sits at the extreme end of the row?

Question

Six persons are seated in a row facing north. Each has a different age, but their order is unknown. Given the following clues:

- C sits 3rd from one end.
- The person who is 12 years old sits 2nd to the right of C.
- The number of persons to the right of the 12-year-old is equal to the number of persons to the left of D.
- O sits 2nd to the right of the person who is 6 years old.
- Two persons sit between D and B, and B's age is twice that of D.
- N sits to the right of P.
- The person who is 36 years old sits 3rd to the left of the person who is 15 years old.
- O is 18 years old.

**Question:** Who sits at the extreme end of the row?

Accepted Answer

**Solution:**

1. Since C sits 3rd from one end, there are two possibilities:
   - C is 3rd from the left end (positions: 1 2 C 4 5 6)
   - C is 3rd from the right end (positions: 1 2 3 C 5 6)

2. The 12-year-old sits 2nd to the right of C.
   - If C is 3rd from left, then 12-year-old is at position 5.
   - If C is 3rd from right, then 12-year-old is at position 1 (which is not possible since 12-year-old must be to the right of C).

So, C is 3rd from the left, and 12-year-old is at position 5.

3. The number of persons to the right of the 12-year-old equals the number of persons to the left of D.
   - 12-year-old is at position 5, so persons to the right = 1 (position 6).
   - Therefore, persons to the left of D = 1, so D must be at position 2.

4. O sits 2nd to the right of the person who is 6 years old.
   - Let the 6-year-old be at position x, then O is at position x+2.

5. Two persons sit between D and B, and B's age is twice that of D.
   - D is at position 2, so B can be at position 5 (positions 3 and 4 between them).

6. N sits to the right of P.
   - So P is to the left of N.

7. The person who is 36 years old sits 3rd to the left of the person who is 15 years old.
   - If 15-year-old is at position y, 36-year-old is at position y-3.

8. O is 18 years old.

Now, placing the knowns:
- C at position 3
- D at position 2
- B at position 5
- 12-year-old at position 5 (so B is 12 years old)
- O is 18 years old, and O sits 2nd to the right of 6-year-old.

Since B is at 5 (12 years), and O must be 2nd to the right of 6-year-old, possible positions for 6-year-old and O are:
- 6-year-old at 3, O at 5 (but 5 is B)
- 6-year-old at 4, O at 6

So 6-year-old at 4, O at 6.

N sits to the right of P, so P must be left of N.

The 36-year-old sits 3rd to the left of 15-year-old.
- Possible positions: 36 at 1, 15 at 4.

Assigning:
- Position 1: 36 years old
- Position 4: 15 years old

Positions:
1 - ? (36 years)
2 - D
3 - C
4 - ? (15 years)
5 - B (12 years)
6 - O (18 years)

Since 6-year-old is at 4, and 15-year-old is at 4, this conflicts. So 6-year-old must be at 1, O at 3.

But O is at 6 from earlier, so the only consistent arrangement is:
- Position 1: N (36 years)
- Position 2: D
- Position 3: C
- Position 4: P (15 years)
- Position 5: B (12 years)
- Position 6: O (18 years)

N sits to the right of P, so P at 4 and N at 1 contradicts this. So N must be at position 6.

Rearranging:
- Position 1: ? (36 years)
- Position 2: D
- Position 3: C
- Position 4: P (15 years)
- Position 5: B (12 years)
- Position 6: O (18 years)

N must be to the right of P, so N at 5 or 6, P at 4.

Since B is at 5, N must be at 6, but O is at 6.

Hence, N is at position 1 (extreme left).

**Answer:** N sits at the extreme end of the row.

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