The Grid

A PuzzleCritic Original:

An empty 6-by-6 grid of squares is filled with numbers as follows. The first row contains the numbers {1,2,3,4,5,6} in some order. In each subsequent row, the kth number is equal to the position of the number k in the row above. For how many such grids are the first and last rows identical?

Solution

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Weights

From the Tournament of the Towns:

A balance and a set of metal weights are given, with no two the same. If any pair of these weights is placed in the left pan of the balance, then it is always possible to counterbalance them with one or several of the remaining weights placed in the right pan. What is the smallest possible number of weights in the set?

Solution