In a certain code language, ‘MORE’ is coded as ‘14 - 12 - 9 - 22’ and ‘KNOW’ is coded as ‘16 - 13 - 12 - 4’. How will ‘SAID’ be coded in the given language?

Correct — A. Rule: code = 27 - (position of the letter), which is the position of its opposite letter (A and Z, B and Y, and so on).

Check it on MORE:

M = 13 gives 27 - 13 = 14
O = 15 gives 12
R = 18 gives 9
E = 5 gives 22 — the printed code 14 - 12 - 9 - 22.

Now SAID:

S = 19 gives 27 - 19 = 8
A = 1 gives 26
I = 9 gives 18
D = 4 gives 23

The code is 8 - 26 - 18 - 23 — option (a).

Why the others are wrong

• (b)
  8 - 26 - 17 - 23 — The third number 17 would make I the 10th letter. I is the 9th, and 27 - 9 = 18.
• (c)
  7 - 25 - 18 - 23 — 7 and 25 come from subtracting from 26 instead of 27. S is the 19th letter and its opposite is H, the 8th, not the 7th.
• (d)
  7 - 26 - 18 - 22 — Two slips at once: 7 for S (26 - 19 rather than 27 - 19) and 22 for D, where D is 4 and 27 - 4 = 23.

An opposite-letter code replaces a letter by its mirror image in the alphabet: A with Z, B with Y, M with N. Because the pairs sit symmetrically, the two positions always add to 27.

So you never need to count backwards from Z. Take the position, subtract it from 27, and you have the answer.

Both sample words are given for a reason. A single word can fit several rules, and the second word is what tells you whether the code is a fixed shift, a growing shift or a mirror.

Key facts

• Opposite pairs add to 27: A(1) with Z(26), M(13) with N(14), E(5) with V(22).
• KNOW to 16 - 13 - 12 - 4 obeys the same rule, since K is 11 and 27 - 11 = 16.
• S, A, I and D sit at 19, 1, 9 and 4, giving 8, 26, 18 and 23.

Common traps

• Subtracting from 26 instead of 27, which shifts every number by one
• Testing the rule on the first letter only and assuming the rest agree
• Reading the dashes in the code as subtraction signs

No directly related past PYQ was found.