Ranking test – shift and convert ends: 37 boys stand in a row facing the building. Ashwini is 15th from the left end. He moves six places to the right. What is his new position from the right end?
-
A16th
-
B21st
-
C20th
-
D18th
-
ENone of these
Answer
Correct Answer: None of these
Explanation
Introduction / Context:We perform an intra-row shift (left-to-right) and then convert left-rank to right-rank using the standard identity. Facing direction is uniform, so “left/right” are consistent.
Given Data / Assumptions:
- Total N = 37.
- Initial left-rank = 15.
- Shift right by 6 positions ⇒ new left-rank = 21.
Concept / Approach:After the shift, compute new right-rank via: position_from_right = N − position_from_left + 1.
Step-by-Step Solution:
New left-rank = 15 + 6 = 21.Right-rank = 37 − 21 + 1 = 17.Verification / Alternative check:Counting to the right of the new position: there are 16 persons (ranks 22 to 37), so Ashwini is 17th from the right—consistent with the formula.
Why Other Options Are Wrong:16th/18th/20th/21st do not match 17 obtained from the identity and direct counting. Hence, among the given choices, the only accurate selection is “None of these.”
Common Pitfalls:Forgetting the +1 term; misapplying shift direction; assuming facing reverses left/right (it does not change within a single row).
Final Answer:None of these