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 Only Subtraction 
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Posted on: Wed Nov 11, 2015 6:30 pm

Posts: 2
Joined: Wed Oct 07, 2015 8:27 am
Post Only Subtraction
How do you solve the puzzles with only subtraction? This seems to be about the only puzzle type I am often incapable of solving.


Posted on: Wed Nov 11, 2015 11:29 pm

Posts: 199
Joined: Tue May 24, 2011 4:55 pm
Post Re: Only Subtraction
clm once posted an illustrated step-by-step solution of a 7x7 subtractions-only puzzle.

clm's illustrations aren't currently embedded but you can still click on each of the 7 instances of the word "Image", download the images individually to your hard drive and either print them or view them onscreen in your default image viewer while reading clm's solution. Please note that you should rename the illustrations sequentially (either A-G or 1-7) while downloading them to get them sorted in the proper order.

(On the topic of possibly restoring images embedded in older threads, I am going to make a couple of observations shortly in reply to Patrick's recent post "Some older images missing" in the "Bugs and errors" section.)


Posted on: Fri Nov 13, 2015 1:12 am

Posts: 744
Joined: Fri May 13, 2011 6:51 pm
Post Re: Only Subtraction
aquilae wrote:
How do you solve the puzzles with only subtraction? This seems to be about the only puzzle type I am often incapable of solving.

Hi, aquilae, I would suggest the use of the parity rule, which is specially useful, for this type of puzzle. Knowing if a determined cell must be even or odd, or if the sum of two contiguous or not contiguous cells in the same line must also be even or odd is many times a big step.

With respect to the problem of the images dissapearing or not accesible from "ImageShack" (mentioned by bram and Patrick) I must say that this is very discouraging, in my case I have not received any mail from them in this respect, anyway I always thought that the old images were going to be kept "for always", regardless of requiring, in a determined moment, some tax "for the future". My last images were sent via following the Patrick's advise anyway.

Not sure how many of them could be recovered in the coming weeks, in my case I think I have some in my PC, but it is tedious to resend them all, for instance: I wrote the post "Step by step solution for a 7x7 subtractions only" in English and in Spanish (in both Forums).

I am not any expert in computer programming, but another suggestion (though the best solution is the one mentioned by Patrick, that is, storing himself everything): Unfortunately our Forum requires that you upload the images to some web page or "virtual" storage where everyone goes later to download every image, I would have rather preferred the possibility of uploading everything in a simple .pdf document, for instance, easy to prepare and send, and donwload and save by the puzzlers; the option "Print view from Forum" is an alternative for puzzlers to keep it for future reading, etc., but it prints the full thread and not only the specific post, ... .

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Posted on: Fri Nov 13, 2015 11:35 am

Posts: 2503
Joined: Thu May 12, 2011 11:58 pm
Post Re: Only Subtraction
Just a quick note to say that Imageshack offers an app to download all images, which I did by now.

What's left to create is a script that replaces imageshack links in posts automatically..

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