In a certain code language, A + B means ‘A is the husband of B’, A − B means ‘B is the mother of A’, A × B means ‘B is the sister of A’ and A ÷ B means ‘A is the daughter of B’. Based on the above, how is Q related to T if ‘P + Q × R − S ÷ T’?

Correct — B. Two of the four symbols are stated in reverse, and that is the whole difficulty.

Rule: A − B means B is the mother of A, and A × B means B is the sister of A — in both, the second letter is the one being described.

P + Q: P is the husband of Q, so Q is female.
Q × R: R is the sister of Q.
R − S: S is the mother of R, and therefore of Q as well.
S ÷ T: S is the daughter of T.

Q is S's child and S is T's child, so Q is T's granddaughter through a daughter — option (b).

Why the others are wrong

• (a)
  Sister — Sister collapses two generations. Option (a) would need Q and T to share parents, but S sits between them as T's daughter and Q's mother.
• (c)
  Mother’s mother — Option (c) inverts the direction. It would make Q the grandparent of T, whereas S ÷ T reads S is the daughter of T, putting T at the top of the line and Q at the bottom.
• (d)
  Daughter’s husband — Q is female. P + Q states that P is the husband of Q, so option (d) fails on gender before the generations are even counted.

Symbol-coded relation items are decided by one habit: rewrite each symbol as a sentence in the order the paper gives it, before drawing anything.

The trap here is that two of the definitions are stated backwards. A − B says B is the mother of A, not A is the mother of B, and A × B says B is the sister of A. Read them at speed and the family tree comes out upside down.

Gender is carried only by the relation words — husband, mother, sister, daughter. Q is female because P is stated to be her husband, and that single fact settles two of the options.

Key facts

• A + B means A is the husband of B, so the letter before the plus sign is male.
• A − B and A × B both describe the second letter, which is the reversal this item is built on.
• S is the daughter of T and the mother of Q, which places Q two generations below T.
• Q is female, so Q is T's daughter's daughter rather than a grandson.

Common traps

• Reading A − B as A is the mother of B, and building the tree one generation the wrong way up.
• Forgetting that R is only a link in the chain and never appears in the answer.
• Answering granddaughter without checking which of T's children she descends through.

No directly related past PYQ was found.