Unbelievable Math
Wed Feb 25 2004

I admit it, I'm easily amused. I got this from a math group I'm a member of and just had to share it.

I know, I'm a geek.


Here is a math trick so unbelievable that it will stump you.

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 recognize the resulting number?

Someday I'll have to put in here the math card trick I know.

11 Comments
  • From:
    Salamander (Legacy)
    On:
    Wed Feb 25 2004
    Let X = first three numbers of your phone number
    Let Y = last four numbers of your phone number
    Given: 10,000X + Y = your phone number

    Then:

    {[(X x 80) + 1]250 + (Y + Y - 250)}/2 =

    {[(80X + 1)250] + (2Y - 250)}/2 =

    {20,000X + 250 + 2Y - 250}/2 =

    10,000X + Y = your phone number

    *grin*
  • From:
    Cutypops (Legacy)
    On:
    Wed Feb 25 2004
    almost, but our # has slightly more digits in it than i think are provided for by your quiz!
  • From:
    Cutypops (Legacy)
    On:
    Wed Feb 25 2004
    mr cuty just tried it. he got the same result, had to do it twice cos he pressed equals twice...
  • From:
    Cutypops (Legacy)
    On:
    Wed Feb 25 2004
    gives up on Sals explanation; goes to find strong drink
  • From:
    Yarngirl (Legacy)
    On:
    Thu Feb 26 2004
    And imagine, I work (not for much longer!) where 16 year old girls call to tell us their most private medical issues.. in a not so private manner. The things I've heard!!

    It worked for me too. :o)
    Julie
  • From:
    Franisbueno (Legacy)
    On:
    Thu Feb 26 2004
    that was so funny! as to who you are referring to, i'm 99.999% sure i know what said gentleman looks like naked.
    also pretty cool how with the new system you can make people sign in to view... neato skeeto...

    loved the nemo pic, and the math prob, and yes, i have a lab test 8am tomorrow, and molecular bio at 9am on fri- i will be last to do your quiz!

    love ya,
    franbo
  • From:
    Sezrah (Legacy)
    On:
    Thu Feb 26 2004
    oh dear, i have a few people i know who love to talk and talk without really thinking about the fact that i might have other things to be doing, or that i may have just walked in the door after a hard day of work or that i'm about to walk out the door to go somewhere. i'm learning though that there are times i need to be firm and, if reqd, butt into their talking to say that i really need to go but thanks for the call

    the only person i let off the hook is my nana, after all, she deserves to talk to me anytime for as long as she likes ;)

    sez
  • From:
    TraumaMama (Legacy)
    On:
    Thu Feb 26 2004
    Cute trick!
    Re your comment, we do close our cattle gate and let the horses graze our lawn when it is dry. Right now they would leave huge holes as it is so soft. I don't picket my horses, it's too risky. Ponies are okay to picket as they are shorter, but a horse will panic if he gets wrapped up in the rope and injure himself. Unfortunately this is a lesson I learned from experience when I knew better.
    Glad to know I am not the only one stressing over gardening stuff.
  • From:
    MagicWhiskey (Legacy)
    On:
    Thu Feb 26 2004
    Cool beans. I tried it with the phone number for Baskin Robbins.
  • From:
    MehtaBasket (Legacy)
    On:
    Fri Feb 27 2004
    Read MehtaBasket and camuscando. Funny stuff.
  • From:
    Oscar (Legacy)
    On:
    Fri Feb 27 2004
    Here's the skinny on the math thing, as explained by someone who isn't me. I grasp the idea, just not the formula:

    x = phone number
    y = last 4 digits

    (x - y) / 10000 = first 3 numbers

    The whole thing can be boiled down to a simple equation. Start off with:

    (((((((((x - y) / 10000) * 80) + 1) * 250) + y) + y) - 250) / 2)

    The goal is to reduce this back down to x:

    ((((((((x - y) / 125) + 1) * 250) + y) + y) - 250) / 2)

    (((((((x - y) * 2) + 250) + y) + y) - 250) / 2)

    ((((x - y) * 2) + 250 + 2y - 250) / 2)

    ((((x - y) * 2) + 2y) / 2)

    ((x - y) + y)

    x

    They basically just have you go in a big circle, starting with the phone number, subtracting the last 4 digits, dividing by 10000 (which is how you get just the first 3 digits), then take you on a long, drawn out process of remultiplying it by 10000 and adding in the last 4 digits.