Coding-Decoding Questions and Answers

Answer: D

HIGH is coded as 19-23-17-19.

Each letter is replaced by the prime number at its alphabet position. C is the 3rd letter and the 3rd prime is 5; A gives the 1st prime 2; G the 7th prime 17; E the 5th prime 11. That reproduces 5-2-17-11 for CAGE, and HIDE gives the 8th, 9th, 4th and 5th primes, 19-23-7-11.

For HIGH: H is the 8th letter (19), I the 9th (23), G the 7th (17), H again 19. Of the other codes, 5-17-1-2 and 13-3-1-2 do not begin with H's code 19, and 17-19-13-17 uses the primes for G, H and F.

Answer: B

P* is P R T O Q S U.

Number the letters by their positions round the clock: O 0, P 1, Q 2, R 3, S 4, T 5, U 6, V 7, W 8, X 9, Y 10, Z 11.

• O* = O Q S Z P R T is positions 0, 2, 4, 11, 1, 3, 5.
• X* = X Z P W Y O Q is positions 9, 11, 1, 8, 10, 0, 2.

Both follow one rule: start at the letter, take the next two by steps of two, then go back one place from the start and again take three letters by steps of two. In offsets from the start: 0, +2, +4, -1, +1, +3, +5.

For P (position 1) this gives 1, 3, 5, 0, 2, 4, 6: P R T O Q S U. The other options do not keep the offsets: P U W ... starts with a step of five, and P S U ... with a step of three.

Answer: B

The answer is P R T O Q S U.

On the clock the letters run O, P, Q, ..., Z clockwise, one per hour mark. Read O* by steps around the clock: O, then +2 (Q), +4 (S), then one place behind O (Z), then +1 (P), +3 (R), +5 (T). X* follows the same rule from X: X, Z (+2), P (+4), W (-1), Y (+1), O (+3), Q (+5).

Applying it to P: P, R (+2), T (+4), O (-1), Q (+1), S (+3), U (+5), which gives P R T O Q S U.

P U W R T V X starts with a jump of 5; P T V Q S U W starts with a jump of 4; P S U P R T V repeats P and starts with a jump of 3. None follows the +2, +4, -1, +1, +3, +5 pattern.

Answer: D

The value of x is 312923.

The letters of WAITER are taken in pairs and the alphabet positions of each pair are added: W (23) + A (1) = 24, I (9) + T (20) = 29, E (5) + R (18) = 23, giving 242923.

Apply the same rule to JUMPER:

\[ \begin{aligned} J + U &= 10 + 21 = 31 \\ M + P &= 13 + 16 = 29 \\ E + R &= 5 + 18 = 23 \end{aligned} \]

That gives 312923. The other options share the ending 2923 or 23 but have the wrong first pair, or a wrong middle pair (212623).

Answer: A

The letter that occurs more than once is D.

In CATER the vowels A and E move to the previous letter, and the consonants C, T and R move to the next letter:

C to D, A to Z, T to U, E to D, R to S, giving the new word DZUDS.

D appears twice (from C and from E). S, Z and U each appear once.

Answer: C

19351 is coded as 2186102.

Each digit is doubled and the results are written side by side. For 28374: 2 to 4, 8 to 16, 3 to 6, 7 to 14, 4 to 8, giving 4 16 6 14 8 = 4166148.

For 19351: 1 to 2, 9 to 18, 3 to 6, 5 to 10, 1 to 2, giving 2 18 6 10 2 = 2186102.

2186211 and 2180619 go wrong in the last digits, and 2816620 reorders the digits.

Answer: C

TON is written as SMK.

Compare PEN with OCK letter by letter: P moves back 1 to O, E back 2 to C, and N back 3 to K. ZEN to YCK follows the same rule: Z back 1 to Y, E back 2 to C, N back 3 to K.

For TON: T back 1 is S, O back 2 is M, N back 3 is K, giving SMK.

SNK moves O back only 1, RMK moves T back 2, and RNJ shifts every letter by the wrong amount.

Answer: A

The colour of the sky is called Pink.

The sky is blue. In the code, the word used for the colour blue is the one that 'means' blue, and the statement 'pink means blue' tells us that the colour blue is called pink.

The trap is to read 'blue means white' and answer white, or to answer blue itself. In these coded-language questions the answer is the code word for the real colour, and only 'pink' is given the meaning blue.

Answer: C

Statement I is true but Statement II is false.

Apply the rule: shift each letter forward by 2, then reverse the order.

CAT: C+2 = E, A+2 = C, T+2 = V, giving ECV; reversed, VCE. Statement I is true.

DOG: D+2 = F, O+2 = Q, G+2 = I, giving FQI; reversed, IQF. The statement says HQF, which uses G+1 = H for the last letter, so Statement II is false.

Answer: B

Only two pairs are correctly matched.

Pair 1, with A = 1, B = 2 and so on: C + A + T = 3 + 1 + 20 = 24. Correct.

Pair 2 reverses the alphabet, Z = 1, Y = 2, so a letter at position p gets \(27 - p\): B = 25, A = 26, T = 7, and BAT = 58, not 25. Incorrect.

Pair 3: R + A + T = 18 + 1 + 20 = 39. Correct.

The trap in pair 2 is to read B = 25 and stop; the code is the sum of all three letters.