Sunday, October 28, 2012

The Mathematics of The Multigram

Anagrams
Part Two
I first decided to write a blog about puzzling when I came across a really tough word problem based on anagrams. It's from Mensa's The Genius Test, which is well worth a look if you're looking for a challenge.

Today we learn all about the multigram puzzle and how numbers help us solve puzzles about letters.



I hope you managed to solve the anagram from WordSmith's brilliant invention we'll be using those skills again today.

Unlike a normal anagram this puzzle had sets of letters grouped by their position in a series of words. The order of the groups, and then the individual words had to be worked out by the solver. There doesn't appear to be a technical name for this kind of puzzle, so I think of them as Multigrams. Here's the multigram that almost caught me out.



An Artistic Multigram







These multigrams required a whole new strategy to solve since, until I had worked out the order of the letter groups, I couldn't begin to work on digraph and trigraph frequency. Yet again the strategy involved playing the odds, with five words to work with it seemed plausible that knowing which letters came up most commonly in which position in a word would be helpful.


The 20 most common initial letters in a word are, in order of frequency:

T O A W B C D S F M R H Y I E G L N O U J

Notable amongst those is the letter E, most common in the language but quite rare at the head of a word.

If we give each letter a score based in it's position in the frequency table, we can see which group is most likely to be the first group. The score's here are equal to the position in the tabe, so we're looking for a low number - lots of letters near the start of the frequency table.

Group 1 - 57
Group 2 - 56
Group 3 - 70
Group 4 - 26
Group 5 - 69

A word of warning here, puzzle setters know all the information that you can lay your hands on, and have usually worked out a strategy for solving a puzzle and thwarted it in advance. That being said, the total for Group 4 is very, very low - as is someone intended it to be that way. However it does seem reasonable to presume that Group 3 and Group 5 must come elsewhere in their respective words, at least for now.

Here are the most common second letters of words, it's a much smaller group so might give some insight. All the vowels are early on in thus group, and a vowel heavy group is always a good bet for second letters.

H O E I A U R N T

Group 1 - 57; 42
Group 2 - 56; 42
Group 3 - 70; 22
Group 4 - 26; 44
Group 5 - 69; 39

So perhaps Group 2 or 3 takes second place; Group 2 looked good for first place as well.

For the third letter it's a shorter group still:

E S A R N I

Group 1 - 57; 42; 35
Group 2 - 56; 42; 31
Group 3 - 70; 22; 17
Group 4 - 26; 44; 32
Group 5 - 69; 39; 29

Group 3 looks like a good choice for third place, that leaves group 2 in second place and Group 1 at the head of the word.

If our intuition and frequency scores have served us well, we have reduced the number of possible permutations of the groups from 120 to 12 and we have another frequency test up our sleeves.

The last letter in a word table looks like this:

E S T D N R Y F L O G H A K M P U W

Group 1 - 57; 42; 35; 77
Group 2 - 56; 42; 31; 74
Group 3 - 70; 22; 17; 33
Group 4 - 26; 44; 32; 40
Group 5 - 69; 39; 29; 51

Since we've already seen that Group 3 looks right in position 3, it looks like Group 4 might come last, leaving Group 5 in the 4th position.

Let's give it a try and see what we've come up with.



Now, having solved this puzzle once before, I'll leave it to you do decipher the five words. They all have something to do with The Arts.

Here's a second multigram for you to have a crack at from scratch and until next time, keep puzzling.



A Mysterious Multigram







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