Work this out.

[kleefarr]

1. Grab a calculator. (You won't be able to do this one in your head)
2. Key in the first three digits of your phone number (NOT the area code)
3. Multiply by 80
4. Add 1
5. Multiply by 250
6. Add the last 4 digits of your phone number
7. Add the last 4 digits of your phone number again.
8. Subtract 250
9. Divide number by 2

Do you recognise the answer?

 

[Analoguesat]

1. Grab a calculator. (You won't be able to do this one in your head)
2. Key in the first three digits of your phone number (NOT the area code)
3. Multiply by 80
4. Add 1
5. Multiply by 250
6. Add the last 4 digits of your phone number
7. Add the last 4 digits of your phone number again.
8. Subtract 250
9. Divide number by 2

Do you recognise the answer?

Doesnt work for me - I end up with a 7 digit number not a 6 digit number!

 

[Topper]

I also end up with a 7 digit number but my telephone number only has 6 digits
!

 

[Analoguesat]

Not one of your better ones kleefar - thats a 100% failure rate so far!!! ;)

Id say it wont work on anything less than a 7 digit phone number as when I tried it using our old 4 digit number from years ago, I ended up with a 7 digit final number

 

[RedAltoGL]

Do you recognise the answer? No!
Perhaps you recognise the number 344***?
Redmund

Ive edited the number as anyone reversing the process can work out your phone number (assuming you started with your actual number.)

 

[Topper]

Do you recognise the answer? No!
Perhaps you recognise the number 344***?
Redmund

Now you lost me RedAltoGL

 

[rolfw]

Worked for me, but then I have a seven digit number.

 

[Topper]

Worked for me, but then I have a seven digit number.

I suppose that I shouldn't have expected anything else really.... we are just not part of the inner sanctum 'cos we live north of Watford...lol

Contrary to popular belief there is life of a sort but alas only 6 digit telephone numbers.

 

[kleefarr]

Um.. I tried it on three tel numbers and all worked. admittedly they were all seven digit without the std/area code. I also tried it on a six digit and got an extra digit in there.
So it seems that this only works for seven digit tel numbers. I wonder if it would work for an eight digit one?
Not bad when it does work though.

 

[kleefarr]

Not one of your better ones kleefar - thats a 100% failure rate so far!!! ;)

Thanks. I take it from that remark, most of the other ones are reasonably good? Pleased to know that they bring a smile to some faces.

 

[RedAltoGL]

Dear Mr Analoguesat
Thank you for "Ive edited the number as anyone reversing the process can work out your phone number (assuming you started with your actual number.)

Last edited by Analoguesat : 11 Hours Ago at 10:42 PM. "

But I used my old works number to come up with that answer, different exchange, not even a London code.

Still it's a good thread, back to putting up a car port before it gets too hot to work.
Regards Redmund

 

[RedDevil_UK]

ummm my number is 6 digit, and i ended up with a 5 digit number lol

 

[Simba27]

Just simple high-school algebra.

Assume your phone number is 123 4567. This can be thought of as (123 x 10000) + 4567. Now let A=123 (first three digits) and B=4567 (last three digits) and write it up as an equation:

( 250 x ((80 x A) + 1) + B + B - 250 ) / 2 = (A x 10000) + B

Multiply both sides by 2:

250 x ((80 x A) + 1) + B + B - 250 = (A x 20000) + (2 x

Multiply out the brackets on the left hand side:

(A x 20000) + 250 + (2 x - 250 = (A x 20000) + (2 x

Simplify again:

(A x 20000) + (2 x = (A x 20000) + (2 x

Proving that this will work for any seven digit number.

 

[kleefarr]

Excellent analysis. Can you sort one out for the 5 & 6 number people?

;)

 

[sligoman]

well for those of you with 6 digits just put a 0 on the end of your telephone number worked for me that way

 

[Simba27]

Either put zeros in front of the number, or modify the equation slightly:

For a six digit number, break it in two parts. A=first three, B=last three. The phone number is A x 1000 + B. Then change the factors to make 1000 rather than 10000. Use 25 x 8 rather than 250 x 8.


ie.
Take the first three digits and multiply by 80. Add 1. Multiply by 25. Add the last three digits. Add the last three digits again. Subtract 25. Divide by 2.

(25((80A)+1)+B+B-25)/2 = 1000A+B
(2000A+25+2B-25)/2 = 1000A+B

For 5 digits, make A the first three, B the last two and change the 80 to an 8.
(25(8A+1)+B+B-25)/2=100A+B