Check Sum For Calculations

[+JohnTee]

Cachers are given a lat and long in the format of N37 12.XXX W89 34.XXX. To fill in the 'X' they have to obtain information that will give them numbers to manipulate, i.e. 925 - 395 = 550 + 37 = 567 = the last three digits of the north coord. Or, three seperate numbers obtained as (a - 1), (b - 2) and (c - 3) = 123.

 

How do I create a check sum that does not give away the three numbers? If I just say add your answer to 433 and you should get 1000 . . . all you have to do is subtract 430 from 1000 to get 567.

 

JohnTee

[+BBWolf+3Pigs]

One I saw is they must add each of the digits together. Then add the digits of that answer, repeating until a single digit is achieved:

 

Answer is: 12345; So 1+2=3+4+5 = 15; 1+5 = 6. Checksum is 6. Not perfect, but it should work, and it's pretty simple.

[+JohnTee]

One I saw is they must add each of the digits together. Then add the digits of that answer, repeating until a single digit is achieved:

 

Answer is: 12345; So 1+2=3+4+5 = 15; 1+5 = 6. Checksum is 6. Not perfect, but it should work, and it's pretty simple.

 

BBWolf - Thanks! I had seen that in a previous forum posting. Tried searching on "check sum" and didn't get anything back. Posting here was the next solution - and it worked!

 

That will work perfect for both sets of numbers.

 

JohnTee

[+Prime Suspect]

Cachers are given a lat and long in the format of N37 12.XXX W89 34.XXX. To fill in the 'X' they have to obtain information that will give them numbers to manipulate, i.e. 925 - 395 = 550 + 37 = 567 = the last three digits of the north coord. Or, three seperate numbers obtained as (a - 1), (b - 2) and (c - 3) = 123.

 

How do I create a check sum that does not give away the three numbers? If I just say add your answer to 433 and you should get 1000 . . . all you have to do is subtract 430 from 1000 to get 567.

 

JohnTee

 

You don't need a checksum.

[+JohnTee]

 

How do I create a check sum that does not give away the three numbers? If I just say add your answer to 433 and you should get 1000 . . . all you have to do is subtract 430 from 1000 to get 567.

 

JohnTee

 

You don't need a checksum.

 

Thanks for the reply Prime Suspect. I checked out evince . . . That's really cool. Handier than pockets on a shirt. The only problem I see with it, for this particular cache I'm working on, is unless somebody has internet access in the field, they would have to answer the clues (which has to be done on-site), go to a computer someplace, then return to the site.

 

I AM going to keep this bookmarked, in the event I do a cache where clues are gathered off-site.

 

JohnTee

[gerboa]

My "checksum" is to ask the cachers to go to the calculated and if they can't see "whatever + whatever1..."

they are SOL and best go back and refigger.

The numbers I use are far greater than .xxx min.

 

Also where I have set general knowledge along the route, advise them to take a handphone to call a mate with access to google.

 

Often I make the calculations meaningless, so that a pre calculator cacher, can spot that the manipulation of the numbers say divide by 10^10 and add to given loc makes no odds.

 

Also if they have to calculate the area of say a round helipad, i ensure that whatever their result, after measuring the diameter by pacing say, that as long as they are in the ballpark the calc will be OK.

 

But I do like the idea of checksums

[+Prime Suspect]

 

How do I create a check sum that does not give away the three numbers? If I just say add your answer to 433 and you should get 1000 . . . all you have to do is subtract 430 from 1000 to get 567.

 

JohnTee

 

You don't need a checksum.

 

Thanks for the reply Prime Suspect. I checked out evince . . . That's really cool. Handier than pockets on a shirt. The only problem I see with it, for this particular cache I'm working on, is unless somebody has internet access in the field, they would have to answer the clues (which has to be done on-site), go to a computer someplace, then return to the site.

 

I AM going to keep this bookmarked, in the event I do a cache where clues are gathered off-site.

 

JohnTee

 

You're right about that. Most puzzle caches are solved before heading out to find the cache. But evince won't be much use for those that need to be solved in the field.

[CoyoteRed]

One I saw is they must add each of the digits together. Then add the digits of that answer, repeating until a single digit is achieved:

 

Answer is: 12345; So 1+2=3+4+5 = 15; 1+5 = 6. Checksum is 6. Not perfect, but it should work, and it's pretty simple.

 

I'm thinking the multiple steps are not needed and only add a level of un-necessary complexity. Both the basic checksum and the reduced checksum have the same weaknesses. This weakness is if there is one number missing you can figure it out by working the checksum with the numbers you have and the difference from your solution and the given checksum is the missing number.

 

EDIT TO ADD: I meant to say that I see no advantage to reducing the checksum down to a single digit.

Edited March 20, 2006 by CoyoteRed

[+JohnTee]

From the 'For What It's Worth' Department . . . Here's the cache that spawned the OP

 

Farkleberry Knob Micro

 

JohnTee

[+larsl]

I like this checksum: http://www.geocaching.com/seek/cache_detai...18-49f24aedcfb7