Discussion questions
Choose a section to work through its questions and solutions. Your progress is shared across pages. Ranges follow collection order; original source labels are kept on each question.
Section 1 · Questions 1–6
Count numbers by their number of digits · Count possible phone numbers before excluding the correct one · +4 more
- Question 1 · Count numbers by their number of digits
- Question 2 · Count possible phone numbers before excluding the correct one
- Question 3 · Divide by permutations of indistinguishable groups
- Question 4 · Choose letters and then account for their order
- Question 5 · Separate disjoint cases from inclusion–exclusion
- Question 6 · Keep a fixed-order block and separate two books
Section 2 · Questions 7–12
Count signals by their remaining colour multiplicities · Distinguish circular rotations from numbered seats · +4 more
- Question 7 · Count signals by their remaining colour multiplicities
- Question 8 · Distinguish circular rotations from numbered seats
- Question 9 · Separate repeated-ball selections into disjoint cases
- Question 10 · Classify code words by the number of repeated pairs
- Question 11 · Count nonempty subsets and a selection with tomatoes fixed
- Question 12 · Keep all ten seats when people are absent
Section 3 · Question 13
Join overlapping card blocks before arranging the remaining cards