Coding-Decoding Questions with Answers: Tricks and 10 MCQs

Coding-decoding questions give you a rule hidden in an example, and ask you to apply it to a new word. They are quick marks in the reasoning section of JKSSB and SSC exams once you recognise the pattern.

The five patterns

• Letter shift: every letter moves the same number of places ahead or back. CAT → DBU is +1\n- Opposite letters: A↔Z, B↔Y, C↔X and so on. CAT → XZG\n- Position values: letters become their numbers. TEA → 20-5-1\n- Reversal: the word is written backwards, sometimes with a shift added\n- Mixed shifts: odd positions move one amount and even positions another

A method that works

1. Compare the first letter of the example with its code, and find the shift (count on your fingers or note the numbers)\n2. Check the second letter to see whether the shift is the same\n3. If it changes in a pattern, you have a mixed-shift code\n4. Apply the rule to the new word letter by letter

Worked examples for each pattern

• Letter shift: if each letter moves two places forward, BOOK becomes DQQM, because B + 2 = D, O + 2 = Q and K + 2 = M
• Opposite letters: replace each letter with the one at the same distance from the other end of the alphabet. DOG becomes WLT, because D and W, O and L, and G and T each add up to 27 in position
• Position values: if letters are replaced by their positions, FACE becomes 6-1-3-5. Decoding works the same way in reverse, so 3-15-13-5 is COME
• Reversal with a shift: reverse PEN to get NEP, then move each letter one place forward to get OFQ
• Mixed shifts: if odd-numbered letters move one place forward and even-numbered letters one place back, MANGO becomes NZOFP. Notice that A moving back wraps round to Z

Number and symbol coding

Some questions give a code for several words and ask you to find the code of a new word by comparing common words. If 'red apple' is coded 'ka lo' and 'red ball' is 'ka mi', then 'ka' means 'red'. Always find the common word and the common code first, then eliminate. A second type gives the sum of letter positions. For example, if CAB = 3 + 1 + 2 = 6, then you can compute any word the same way. Check the arithmetic twice, because a single slip changes the answer.

Decoding questions

A decoding question gives you the code and asks for the word. The method is simply the reverse of the rule. If the code was made by moving each letter two places forward, you move each letter in the code two places back. Write the rule on your rough sheet before you start so that you do not apply it in the wrong direction.

How to speed up

• Learn the alphabet positions up to 26 until you can recall them instantly, and memorise the five letters that are worth 5, 10, 15, 20 and 25 (E, J, O, T, Y)
• Learn the opposite-letter pairs by heart: A-Z, B-Y, C-X, D-W, E-V, F-U, G-T, H-S, I-R, J-Q, K-P, L-O, M-N
• Check two letters of the code before you decide on a rule. A rule that works for one letter may be a coincidence
• If the shift seems irregular, test an alternating pattern before you give up

Common mistakes

• Forgetting that the alphabet wraps, so Z + 1 is A and A − 1 is Z
• Applying the rule to the wrong word in the question
• Counting the starting letter as a step
• Spending more than a minute on a single code. If the pattern is not clear in 40 seconds, mark the question and move on

How much time to spend

Most coding-decoding questions should take 30 to 45 seconds once you know the five patterns. In a timed set of 10 questions, aim for about six minutes. Keep a list of the codes that fooled you and test yourself on them again after a week.

Practise

Try the 10 MCQs below, then continue with coding-decoding practice sets for Junior Assistant and Class-IV. See also the SI reasoning guide and analogy MCQs.