Coding-Decoding Questions and Answers

Answer: C

On the key's pattern, BUS = 30.

The pattern that fits both words is 10 for each letter: TRAIN has 5 letters, so \(5 \times 10 = 50\), and BUS has 3 letters, so \(3 \times 10 = 30\).

The other common coding rule, adding alphabet positions, does not fit: TRAIN would be \(20 + 18 + 1 + 9 + 14 = 62\), not 50. For BUS it would give 42, which is not an option either; 40, 44 and 46 fit no consistent rule.

Answer: C

ATTENTION is coded as 677147234.

Read the letter codes off the two given words, position by position:

• NATION = 467234: N = 4, A = 6, T = 7, I = 2, O = 3.
• EARN = 1654: E = 1, A = 6, R = 5, N = 4.

Then ATTENTION, letter by letter: A 6, T 7, T 7, E 1, N 4, T 7, I 2, O 3, N 4, which is 677147234.

67756154 has only eight digits for nine letters and uses 5 (the code for R). 677142743 scrambles the last digits. Since an exact match exists, 'None of these' is wrong.

Answer: B

Fish swim in air.

Fish swim in water, so the answer is whatever 'water' is called in this code. The chain says water is called air, so in this language fish swim in 'air'.

'Water' is the real-world answer, but in the code 'water' is the name for rain. 'Blue' is what air is called, one step too far along the chain, and 'green' is what tree is called. The trick in such questions is to find the real answer first, then replace it with its code name.

Answer: B

C. S. I. R. stands for 3, 19, 9, 18.

The code is the position of each letter in the alphabet: U = 21, P = 16, S = 19, C = 3, which is exactly 21, 16, 19, 3.

Applying it to CSIR gives C = 3, S = 19, I = 9, R = 18. The option 3, 19, 16, 21 reuses numbers from UPSC, 3, 9, 18, 19 puts the right numbers in sorted order rather than letter order, and 3, 16, 21, 19 borrows the values of P and U from UPSC, letters that are not in CSIR.

Answer: A

NEED is written as MDDC.

Compare DEFENCE with CDEDMBD letter by letter: D→C, E→D, F→E, E→D, N→M, C→B, E→D. Every letter is replaced by the one just before it in the alphabet.

Applying the same rule to NEED: N→M, E→D, E→D, D→C, giving MDDC. MCDC, MCCD and MDCC all contain the right letters in a scrambled order, so they fail the letter-by-letter check.

Answer: C

RAIL is written as 8247.

Each letter has its own digit, in the same position. From RISE = 8419 and MEAL = 5927:

\[ \begin{aligned} R &= 8,\ I = 4,\ S = 1,\ E = 9 \\ M &= 5,\ A = 2,\ L = 7 \end{aligned} \]

E is 9 in both words, which confirms the letter-by-letter rule. So RAIL is R, A, I, L = 8, 2, 4, 7, that is 8247.

8429 swaps A and I and ends in E's digit, 8124 uses S's digit for A, and 8412 puts the digits in the wrong order.

Answer: B

TAP is coded WDS.

Each letter of BUS moves three places forward in the alphabet: B → E, U → X, S → V, giving EXV.

Applying the same rule to TAP: T → W, A → D, P → S, which gives WDS.

The other options use the right letters in the wrong order (WSD, DSW) or shift some letters backwards (SDW), so they do not follow the pattern.

Shifting each letter by the same fixed number of places is the simplest kind of letter code; always test the rule on every letter of the given pair before applying it.

Answer: B

LAME is coded as MBNF.

Compare WORK with XPSL: each letter moves one step forward in the alphabet (W to X, O to P, R to S, K to L).

Apply the same rule to LAME: L to M, A to B, M to N, E to F, giving MBNF. BFNM and FMNB use the right letters in the wrong order, so 'None of these' is wrong too.

Checking one letter is enough to rule out most options: L must become M, and only MBNF starts with M.

Answer: A

The code for OBSERVE is 86.

Each letter is coded by its position in the alphabet, and a word by the sum. Check: F = 6, and JOY = 10 + 15 + 25 = 50. So

\[ \begin{aligned} \text{OBSERVE} &= 15 + 2 + 19 + 5 + 18 + 22 + 5 \\ &= 86 \end{aligned} \]

76, 66 and 56 are each 10 less than the next, the result of slips in adding up the seven letters.

Checking the given examples first (F = 6 confirms simple alphabet positions) is the quickest way to find the coding rule.

Answer: B

GOOD LUCK is written as IQQF NWEM.

Each letter moves two places forward in the alphabet: H to J, A to C, R to T, D to F gives JCTF for HARD, and W to Y, O to Q, R to T, K to M gives YQTM for WORK. In PAYS the P, A and S follow the same rule (R, C, U).

Applying +2 to GOOD LUCK: G to I, O to Q, O to Q, D to F gives IQQF, and L to N, U to W, C to E, K to M gives NWEM. Options with IQQU shift D wrongly, and those ending in Q shift K wrongly.