Bob Scott
@tunelabguy.bsky.social
Software developer of piano tuning applications.
Here is a proof. The 5x4 rectangle with 20 spaces must be tiled with exactly 4 "X"s. In an end column of the 5x4 we find 5 spaces where no two of them can be covered by the same "X" without some part of the "X" going outside the 5x4. Therefore not even the one column can be covered by 4 Xs.
February 5, 2025 at 12:51 AM
Here is a proof. The 5x4 rectangle with 20 spaces must be tiled with exactly 4 "X"s. In an end column of the 5x4 we find 5 spaces where no two of them can be covered by the same "X" without some part of the "X" going outside the 5x4. Therefore not even the one column can be covered by 4 Xs.