Some teasers concerning conditional probabilities

[1]  Thomas L. Saaty,et al.  Foresight—Insight—Hindsight , 1979 .

[2]  I. G. Betteley.  Ambiguity in probability problems , 1979, The Mathematical Gazette.

[3]  John E. Freund,et al.  Puzzle or Paradox , 1965 .