Math Trickery

Every now and then, spam gets through. Usually junk, but today, this showed up attached to a penis enhancement spam. Don't ask me why, even the image was part of the email, but play along. It's trippy.

Grab a calculator (You won’t be able to do this in your head)
Key in the first three digits of your phone number (not your area code)
Multiply by 80.
Add 1.
Multiply by 250.
Add the last 4 digits of your phone number.
Add the last 4 digits of your phone number again.
Subtract 250.
Divide number by 2
Does the answer look familiar?

"It is pointless to resist, my son." -- Darth Vader
"Resistance is futile." -- The Borg
"Mother's coming for me in the dragon ships. I don't like these itchy clothes, but I have to wear them or it frightens the fish." -- Thurindil

Well. I guess that's that then.

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Posted on Aug 14, 2010 11:08 pm by Samson in: | 15 comment(s) [Closed]
LOL thats cool.

Very cute. You really have to wonder at how much time someone's gotta have on their hands to come up with some of these math tricks.

Anonymous (Dallen) [Anon] said:
Comment #3 Aug 16, 2010 2:32 pm
Sorry, I don't get it. It just comes back with "a number" for me. The only consitency is it's always a 5 digit number.

Pretty good chance it only works with US phone numbers, or other systems that also use 7 digits for the local number.

If you are in Australia start with the first 4 instead of 3, works the same.

It should always return a 7 digit number, Dallen.. :huh:

You'd think that even for non-US numbers it'd still return the seven digits.. unless, are you folks just dropping your country code and ending up with a five digit number to work with? That probably would screw the math. Samson, I guess we need to find you a math trick along the same lines that also works for the full 10 digit phone numbers, even if the first digit is 0. ;)

Good to hear there's a way to make it work for telephone numbers that are the same length as those used in Australia. I'd expect that solution to work for most of the phone numbers outside the US.

Anonymous [Anon] said:
Comment #7 Aug 17, 2010 12:45 am
first digits = lll
last digits = rrrr

The spam recipe says:

((lll * 80 + 1 ) * 250 + (2 * rrrr) - 250) / 2

+1 * 250 and -250 cancel each other:

((lll * 80) * 250 + (2 * rrrr) / 2

80 = 40 * 2 and * 2 and / 2 cancel each other:

((lll * 40) * 250 + (rrrr)


lll * 40 * 250 + rrrr

simplify: 40 * 250 = 10000
In decimal base, multiplying a number with a power of 10 simply shifts the number to the left

lll * 10000 + rrrr = lll0000 + rrrr = lllrrrr

Well, I suspect that explaining the math behind it probably takes most of the fun out of it, but yes, that's why it "works". The issue is why isn't it working for non-US folks has to come down to their phone numbers not being the same length (because of country codes), so shifting the first three digits four places left.. this should be getting obvious by now, no?

Anonymous (Dallen) [Anon] said:
Comment #9 Aug 17, 2010 1:55 pm
I got it to work, i must have just not pushed one button or another hard enough. I have a US phone number btw.

I knew there had to be something wrong when you said it'd returned a 5 digit number. :lol:

Anonymous [Anon] said:
Comment #11 Sep 8, 2010 3:32 pm
In Australia, our numbers are 10 digits (8 without the 04 code) ... the number at the end was mising a number in the middle xD

I guess the trick for you folks down under then is to pretend that you're in America and just use the last seven of your phone number for this one. ;)

Anonymous [Anon] said:
Comment #13 Sep 8, 2010 10:07 pm
It looked familiar, but since I have an 8 digit number the "magic" didn't quite work...

PetrusOctavianus [Anon] said:
Comment #14 Sep 8, 2010 10:07 pm
Previous comment was from me.

Well, it's not whoever created this particular math trick's fault that you live in the Land Down Under. :P

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