P + Q means P is the husband of Q, P − Q means P is the sister of Q, P × Q means P is the mother of Q. Then what does A × B + C mean?

Correct — A. Read the expression one symbol at a time, through the shared letter.

Rule: + = husband of, − = sister of, × = mother of.

A × B → A is the mother of B
B + C → B is the husband of C, so C is B's wife
A is the mother of C's husband → mother-in-law of C

That is option (a).

Why the others are wrong

• (b)
  A is mother of C — Mother of C would need C to be A's child. C is the wife of A's son B, so A is her mother only by marriage.
• (c)
  A is sister-in-law of C — Sister-in-law would need A to be B's sister, the − symbol. The expression joins A and B with ×, which makes A B's mother.
• (d)
  A is grandmother of C — Grandmother would need C to be B's child. The + sign makes B the husband of C, so C is in B's generation, not below it.

In a coded relation each symbol links the two letters on either side of it. Decode pair by pair: A × B, then B + C, joined through the shared letter B.

The chain here runs mother, then husband. A husband's mother is his wife's mother-in-law.

Key facts

• Decode a coded relation pair by pair, through the shared letter.
• A husband's mother is the wife's mother-in-law.
• In this code, P + Q makes P male and Q female.

Common traps

• Stopping at A × B and choosing 'A is mother of C'.
• Mixing up the symbols: reading × as sister gives sister-in-law.

No directly related past PYQ was found.