C, D, E, F, G, H, and I are the father, mother, aunt, brother, sister, wife and daughter of J, but you do not know which is which. But you know that:

  • E and F are the same gender.
  • C and D are of different genders.
  • H was born before C
  • F is not the mother of J.

Referring to the above information, which one of the following must be true?

  • C is female.
  • D is female.
  • E is female.
  • F is male.
  • H is male.
  • 1
    $\begingroup$ I've spent an hour staring at this puzzle so far - I'm utterly stuck. Even a clue would be much appreciated. $\endgroup$ – Contango Jun 12 '13 at 9:13

Note that there are only two males among C, D, E, F, G, H, and I. Now E and F are the same gender. Consider the case that they are male. This would imply rest are female and this would contradict that C and D are of different genders. So E and F should be female

'E is female' must be true


See there are two males among the $7$ persons.

Consider that $E,F$ are males then except $E,F$ all must be females so $C,D$ cannot be of different genders which contradicts the hypothesis so $E,F$ must be females.Thus third option that $E$ is female is necessarily true.

You can easily check that all other options are not necessarily true.


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