Swap in a row — deducing class size and new position Ramesh is 9th from the left; Suman is 6th from the right. After they swap positions, Ramesh becomes 15th from the left. What is Suman’s position from the right then?

Introduction / Context:Swapping two students means each takes the other's exact seat. Use the conversion between left and right indices to find the class size first.

Concept / Approach:If Suman is 6th from the right in a class of N, the same seat is (N − 6 + 1) from the left. After the swap, Ramesh is in that seat and is given as 15th from the left.

Step-by-Step Solution:N − 6 + 1 = 15 ⇒ N − 5 = 15 ⇒ N = 20.Ramesh's original right-rank = N − 9 + 1 = 12 ⇒ that becomes Suman's new right-rank after the swap.

Verification / Alternative check:Left and right ranks always sum to N + 1 = 21 for N = 20 (e.g., 9 + 12 = 21).

Final Answer:12th