The art and craft of problem solving by Paul Zeitz

I got introduced to Paul Zeitz through his great course lectures. The book is very well written. There are number of problems I got introduced by him like Census taker

1. The pill problem
2. Census taker problem
3. Frog jumping
4. Chicken Nugget problem
5. Connecting box problem
6. The locker problem
7. Lock Problem
8. Lock Problem Simulation
9. Symmetry and solution to quartic equation
10. Cat and mouse
11. Cutting sheet so that elephant can pass through it
12. Dishes on lazy susan
13. Why product of 4 consecutive numbers is never a square number ?
14. Climbing Monk Problem
15. Light bulb and 3 switches