Lesson 1 of 2 · Letter shifting / reversal
Plus minus k
Coding-Decoding · for IPMAT Indore, IPMAT Rohtak and JIPMAT · asked in JIPMAT 2025
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The idea of Letter shifting / reversal
In a letter-shift code every letter of the word is moved a fixed or patterned number of places (+1, +2; −2 then +2; +1, +2, +3 …), replaced by its opposite letter (A ↔ Z), or the word is first rearranged (reversed, halves swapped, pairs swapped, letters sorted) and then shifted. Rohtak asked three such items in 2019; JIPMAT asks one or two a year.
The exam method
- Align and subtract. R O A S T over P Q Y U R gives −2, +2, −2, +2, −2: odd positions −2, even positions +2.JIPMAT 2025
- Constant shift? Done. TOWEL → UPXFM is +1 throughout.
- No pattern? Rearrange first. SEQUENCE → FDOFVRFT: reversed, ECNEUQES, then +1. IMTITJU → TMIIUJT: blocks of three reversed around the middle letter.Rohtak 2019
- Opposites. FRUITS → UIFRGH pairs each letter with its mirror (F–U, R–I, T–G, S–H). A code that mixes big jumps (+19, −5 …) is usually the opposite-letter rule.
- Answer by elimination. Code the first two letters of the asked word; usually only one option starts that way.