Rank shifts in a fixed-length row In a row of 21 girls, Monika moves four places to the right and becomes 12th from the left. What was her earlier position from the right end?

Introduction / Context:Row-ranking problems use a fixed total length. Moving within the row changes left/right indices while preserving N (the total count).

Given Data / Assumptions:

• Total N = 21.
• After moving 4 to the right, Monika is 12th from the left.

Concept / Approach:If the new left-rank is 12 after shifting 4 to the right, the earlier left-rank was 12 − 4 = 8. Convert that earlier left-rank to right-rank via N − L + 1.

Step-by-Step Solution:Earlier left-rank = 12 − 4 = 8.Earlier right-rank = 21 − 8 + 1 = 14.

Verification / Alternative check:Positions from left and right should sum to N + 1: 8 + 14 = 22 = 21 + 1.

Why Other Options Are Wrong:They do not satisfy the invariant L + R = N + 1 with earlier L = 8.

Common Pitfalls:Forgetting to adjust by +1 when converting between left and right ranks.

Final Answer:14th