Digit arrangement – Swap positions (1↔6, 2↔7, 3↔8, 4↔9, 5↔10) in the 10-digit string 5904627813. After this paired swap, which digit is fourth from the right end?

Introduction / Context:
This problem tests careful indexing and stable, pairwise swaps. We take the 10-digit sequence 5904627813 and swap positions in fixed pairs: (1↔6), (2↔7), (3↔8), (4↔9), (5↔10). Then we must read the fourth digit from the right of the resulting string.

Given Data / Assumptions:

• Original string (left→right positions 1..10): 5 9 0 4 6 2 7 8 1 3
• Swaps: (1,6), (2,7), (3,8), (4,9), (5,10).
• After swaps, read the 4th digit from the right (i.e., position 7 from the left).

Concept / Approach:
Perform the swaps carefully without cascading errors (treat swaps as simultaneous or track in a copy). After the final arrangement, identify the 4th from right. Alternatively, compute that “4th from right” equals index 10−4+1 = 7 from the left.

Step-by-Step Solution:

Verification / Alternative check:
Count from the right: (1)6, (2)4, (3)0, (4)9 → same result.

Why Other Options Are Wrong:

• 4, 1, 0: Appear in the final string but not at the 4th-from-right position.
• None of these: There is a correct listed option (9).

Common Pitfalls:
Applying swaps in-place in a way that uses already-swapped values; miscounting “4th from right”; or indexing from zero. Work with a copied array or treat swaps as simultaneous.

Final Answer:
9