### Pentominous by Carl Worth

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Theme: F is for Fiendish

Author/Opus: This is the 4th puzzle from guest contributor Carl Worth.

Rules: Divide the grid into 20 pentominoes so that no two pentominoes of the same shape (including rotations/reflections) share an edge. A cell with a letter in it must be part of the pentomino shape normally associated with that letter. An inventory of possible pentominoes is given below the puzzle.

Answer String: Enter the letter associated with the pentomino occupying each cell in the marked rows from left to right and in the marked columns from top to bottom, separating the groups with a comma. Use CAPITAL LETTERS!

Time Standards (highlight to view): Grandmaster = 4:30, Master = 10:00, Expert = 20:00

Solution: PDF

Note: Follow this link for other Pentominous puzzles. If you are new to this puzzle type, here are our easiest Pentominous to get started on.

• Andrew Brecher says:

That was brutal. Seemed like I had to go one square at a time for most of the board.

• Aaron Chan says:

Indeed. The comment about having to go one square at a time is more or less spot on too, at least for determine whether a square is an F.

• Chris Green says:

Nice puzzle but tough! V sbhaq gur orfg jnl gb fbyir guvf qhr gb gur ahzore bs Sf ba gur obneq jnf gb hfr gjb pbybhef – bar sbe “vf S” naq bar sbe “vf abg S” naq gb tb nobhg fbegvat gur “abg S”f vagb cragbzvabf jura V ena bhg bss zbirf gung jnl.

• Jack Bross says:

That’s exactly what I ended up doing. Also, would echo the comment from Jonah about thinking in terms of 3×3 blocks.

• DGPArtist says:

A lot of trial and error here, not sure I really solve this logically.

• Jonah says:

Everyone agrees that F pentominoes are the least intuitive pentomino, right?

I found it easier to think of what 3×3 “blueprint” each F could be a part of.

• Carl W says:

Thanks all, for the comments. I learned something new about the puzzle from the strategies shared here.

And yes, Jonah, the F pentomino is definitely the least intuitive for me. I set out to construct this puzzle specifically to force myself to get more practice at visualing the different possible orientations for that tricksy F.

So hopefully we all got to learn something with this one.

Happy puzzling!

-Carl

• edderiofer says:

Did anyone else notice that the two Fs in column 8 were unnecessary?

In any case, this was certainly a challenging puzzle, and I definitely learned a few things about the F pentomino in the process. There certainly were some parts where I did end up going one square at a time, but I wouldn’t call it “most of the board”. The cascading breakin, pbafvqrevat gur ybjre yrsg Y cragbzvab naq ubj vg vagrenpgf jvgu gur arneol Sf, had me stumped for a bit before I noticed it.

• Carl W says:

I, (for one), didn’t notice those were unnecessary, nor did I have your breakin in mind. I’ll have to go back and try the puzzle with that.

In fact, the original breakin I had in mind when constructing the puzzle did use the two Fs in column 8. And what you used as your breakin was a very late addition to the puzzle to nail down a local section that could have had multiple solutions.

So, I guess that means I spoiled the original idea I was trying to work with. Oh well. I’m glad you still enjoyed it.

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