Chapter 13
Digit problems
1 When can you cancel illegitimately and yet get the correct answer?
2 A multiplication problem
3 A division problem
4 The most famous Monthly problem
5 The problem of 4n’s
Appendix: Squares with 9 distinct nonzero digits
Appendix: Squares with 10 distinct digits
Exercise
Charles Twigg’s square number puzzle
Cross number puzzle