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October and 11 Prime Numbers (Posted on 2024-05-03) Difficulty: 3 of 5
Reconstruct the multiplication:

                               
       * * * * * *         where:  O C T O
               * *                   C T O
      -------------                  C T O B
       * * * * * *                     T O
     * * * * * *                       T O B E
    ---------------                    T O B E R
     O C T O B E R                       O B E R
                                           B E R
                                           B E
                                             E R
                                               R
                           are 11 prime numbers.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution computer solution | Comment 1 of 2
lets='octber';
idx=combinator(10,6,'p');
digsets=idx-1;
digsets=char(digsets+48);
for i=1:length(digsets)
  digs=digsets(i,:);
  for j=1:6
    cmd=sprintf('%s = ''%s'';',lets(j),digs(j));
    eval(cmd);
  end

  pset=["octo";"cto";"ctob";"to";"tobe";"tober";"be";"er";"r"];
  good=true ;
  for w=1:length(pset)
    ns=char(pset(w));
    ns=strrep(ns, 'o', o) ;
    ns=strrep(ns, 'c', c) ;
    ns=strrep(ns, 't', t) ;
    ns=strrep(ns, 'b', b) ;
    ns=strrep(ns, 'e', e) ;
    ns=strrep(ns, 'r', r) ;


    if ~isprime(str2double(ns))
      good = false;
      break
    end
  end
  if good
    disp(digs)
    october=str2double([digs(1:3) o digs(4:6) ]);
    divisors(october)
  end
end




finds the correspondence of letters to digits to be

october
9829173

based upon the primality of the 11 shown numbers,

and october's divisors are

 1    3    29    87   112979   338937   3276391   9829173

so candidates for the multiplication are


    112979   338937
        87       29
    ------  -------    
    790853  3050433     
   903832   677874  
   ------   ------- 
   9829173  9829173
   
The one on the left fits the set of asterisks shown.   

I inadvertently left out two of the primes, but came up with the unique product anyway.

  Posted by Charlie on 2024-05-03 12:54:38
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