| 16 | The bat and the ballThink twice | Easy | Setting up an equationReading carefully | |
| 646 | The striking clockLateral thinking | Easy | Lateral thinking | |
| 648 | The rope ladderLateral thinking | Easy | Lateral thinking | |
| 649 | Twenty-eight daysLateral thinking | Easy | Lateral thinking | |
| 650 | A brick and half a brickLateral thinking | Easy | Lateral thinking | |
| 651 | Cats and miceLateral thinking | Easy | Lateral thinking | |
| 652 | All but nineLateral thinking | Easy | Lateral thinking | |
| 17 | The snail and the wellA gentle trap | Medium | Careful countingWatch the last step | |
| 22 | At least one headProbability surprise | Medium | Conditional probabilityListing cases | |
| 32 | The Monty Hall problemProbability surprise | Medium | Conditional probabilityCounting cases | |
| 33 | The birthday paradoxA likely coincidence | Medium | Complementary countingProbability | |
| 70 | The hundred lockersA surprising pattern | Medium | Divisor countingPerfect squares | |
| 647 | When the hands meetLateral thinking | Medium | Lateral thinking | |