'Pent-up' Frustration

November 2018 : Puzzle

Place as many distinct pentominoes as you want into an 8-by-8 grid, in such a way that the placement is “tight” — i.e., no piece(s) can freely slide around within the grid.

The score for a given placement is the sum of the square roots of the areas of the empty regions in the grid.

What is the largest score you can obtain?

This month, when you send in your entry, please send in your grid. Please use the standard notation, — i.e. F, I, L, N, P, T, U, V, W, X, Y, Z — and use “.” to denote empty spaces. (So the top row in the valid placement example would be “…Z..LL”)