| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Determine the coefficient of linear thermal expansion of the metal tube. What metal the tube could be?
Answer: $13\cdot{10^{-6}}\frac{1}{℃}$