In the word ORGANISATIONAL, the letters are interchanged in pairs in sequence…

2025

In the word ORGANISATIONAL, the letters are interchanged in pairs in sequence (the first and second, the third and fourth, the fifth and sixth, and so on) up to the last letter. In the resulting word, what is the tenth letter from the right end?

  1. A.

    A

  2. B.

    I

  3. C.

    S

  4. D.

    N

Attempted by 34 students.

Show answer & explanation

Correct answer: B

Concept:

This is a positional rearrangement task with two stages. First, build the new word by applying the swap rule from left to right, keeping every letter (no letter is added or lost). Second, locate a position counted from the right: in a word of length n, the k-th letter from the right is the (n - k + 1)-th letter from the left.

Application:

  1. Index the original word: O(1) R(2) G(3) A(4) N(5) I(6) S(7) A(8) T(9) I(10) O(11) N(12) A(13) L(14). It has 14 letters, so the pairs are (1,2)(3,4)(5,6)(7,8)(9,10)(11,12)(13,14).

  2. Swap inside each pair: OR -> RO, GA -> AG, NI -> IN, SA -> AS, TI -> IT, ON -> NO, AL -> LA.

  3. Join the swapped pairs to get the rearranged word: ROAGINASITNOLA (still 14 letters).

  4. Convert the target position: the 10th letter from the right is at position 14 - 10 + 1 = 5 from the left.

  5. Read position 5 of ROAGINASITNOLA: R(1) O(2) A(3) G(4) I(5) - the 5th letter from the left is I.

Cross-check:

Count straight from the right end of ROAGINASITNOLA: A(1) L(2) O(3) N(4) T(5) I(6) S(7) A(8) N(9) I(10). The 10th letter from the right is I, which agrees with the position conversion.

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