Take three and pay for only two with coupon TRIPLEEN

Desmond MacHale is an Irish mathematician who is Emeritus Professor of Mathematics at University College Cork. He is an author and speaker on several subjects, including George Boole, lateral thinking puzzles, and humour. He has published over 80 books, some of which have been translated into languages including Danish, Italian, Norwegian, Spanish, German, Korean, and Japanese.
Desmond MacHale is an Irish mathematician who is Emeritus Professor of Mathematics at University College Cork. He is an author and speaker on several subjects, including George Boole, lateral thinking puzzles, and humour. He has published over 80 books, some of which have been translated into languages including Danish, Italian, Norwegian, Spanish, German, Korean, and Japanese.