This is a civil service examination question, the answer is: Never

Analysis: All three teacups must be turned over three times at a time, which is an odd number of times, and the stipulation must be two. The teacups are flipped together so that the mouths of the teacups face up, so no matter how many times they are turned, the total number of flips is an even number, so it is impossible to make all three teacups face up.

Extended information:

Quantitative relationship problem-solving skills in the Civil Service Examination

1. Quick calculation methods: Substitution and elimination method, multiple characteristic method, assignment method, cross method , First and last digit method

2. Question types: engineering problems, itinerary problems, set problems, plane geometry, function images, proportion problems

3. The first four types of optimal value problems (drawer Principle type, set distribution type, arithmetic extreme value type, geometric extreme value type), permutation and combination (although the difficulty is slightly higher, the frequency is too high, and it is still listed as a five-star test point)

4. It is recommended to win first : Multiple property method, assignment method, proportion problem, engineering problem, cross method, stroke problem, set problem, plane geometry, substitution and elimination method, first and last digit method, function graph, these will take about 16 hours (referring to basic digestion and absorption) time), which can almost guarantee that 60% of the people can do it

5. The next step is the top four most valuable types and permutations and combinations. The top four most valuable types take slightly more time (6 hours), but not Difficult to master; the content of permutations and combinations is moderate but requires high thinking. You can ensure that you can solve the easy questions and general questions first (3 hours).