Required Mathematical Intelligence

Chapter 4 Weighing Parts

There are 13 parts, all of which are exactly the same in appearance, but one is a substandard product, whose weight is different from the others, and its weight is unknown.Please use the balance to weigh 3 times and find it out (this question is more difficult, as long as you can do it, it means that you have extraordinary intelligence. There is no time limit). ]
[Answer: First put 4 parts on each side of the balance. If the balance is balanced, it means that the broken part is in the other 5 parts. It is not difficult to find it after weighing twice.If it is unbalanced, it means that the bad ones are among the 8. At this time, remember which ones are light and which ones are heavy.The remaining 5 are qualified and can be used as standards.Then put 5 qualified ones on the left end of the balance, take 2 light ones, and 3 heavy ones on the right end.At this time, if the right end is low, it means that the bad one is among the three heavy ones, and it can be weighed out at one time.Other situations are relatively simple and will not be repeated here. ]
(End of this chapter)