In a certain code language, ‘DRIVE’ is coded as ‘62749’ and ‘RIDES’ is coded as ‘76284’. What is the code for ‘V’ in that language?

Correct — C. Rule: the code is a set of digits for a set of letters, not a letter-by-letter cipher.

DRIVE uses the letters D, R, I, V, E and the digits 6, 2, 7, 4, 9.
RIDES uses the letters R, I, D, E, S and the digits 7, 6, 2, 8, 4.

The two words share D, R, I and E, and the two codes share 6, 2, 7 and 4.

V is the letter DRIVE has and RIDES does not, and 9 is the digit 62749 has and 76284 does not. So V is coded 9, option (c).

Why the others are wrong

• (a)
  6 — 6 sits in both codes, so it must stand for a letter both words contain — one of D, R, I or E. V appears in DRIVE alone, so it cannot be 6.
• (b)
  8 — 8 appears only in the code for RIDES, so it belongs to S, the letter only RIDES has. V is in the other word entirely.
• (d)
  7 — 7 sits in both codes too, so like 6 it belongs to one of the four shared letters. It cannot code a letter that appears in only one of the words.

This is a set-matching code, not a positional one. Test position first and watch it fail: D is the first letter of DRIVE with code 62749, but D is the third letter of RIDES, where the third digit is 2.

Once position is out, compare the words as sets. Letters common to both words must map to digits common to both codes, and a letter unique to one word must map to the digit unique to that word's code.

That single elimination answers the question without solving the cipher at all.

Key facts

• DRIVE and RIDES share the letters D, R, I and E.
• Their codes 62749 and 76284 share the digits 2, 4, 6 and 7.
• V occurs only in DRIVE and 9 only in its code, so V = 9.
• S occurs only in RIDES and 8 only in its code, so S = 8.

Common traps

• Assuming the digits line up with the letters in the order printed.
• Trying to solve every letter when only one is asked for.
• Reading 62749 as five ordered clues rather than as an unordered set.

No directly related past PYQ was found.