# A Little Math Trick

#### Pappy

##### Member
Here is a math trick that it will stump you.

Personally I would like to know who came up with this and why that person is not running the country.

1. Grab a calculator. (you won&#39;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
5. Multiply by 250
8. Subtract 250
9. Divide number by 2

Do you recognize the answer? :wow:

1

#### 13788

##### Guest
TheaterJunkie: OMG
I just did this & almost fell out of my chair at work
ROFL

Bryan

#### Dude!

##### Just Browsing
Hehehe that&#39;s quite clever

#### Pecker

##### Retired Moderator
It wouldn&#39;t give me the answer. I&#39;m unlisted.

#### jonb

##### Sexy Member
I got 5555554.999975321

Last time I use my friend&#39;s Pentium machine.

#### mindseye

##### Experimental Member
Originally posted by Pappy@Mar 25 2005, 10:06 AM
1. Grab a calculator. (you won&#39;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
5. Multiply by 250
8. Subtract 250
9. Divide number by 2
[post=293919]Quoted post[/post]​

Less impressive when you know that 80 x 250 = 20000. All that&#39;s going on is convoluted algebra to conceal what you&#39;re doing.

Here&#39;s what happens. Say your phone number is ABC-DEFG. (No hooked on phonics jokes, please&#33

Step 1: Display = 0
Step 2: Display = ABC
Step 3: Display = ABC x 80 (whatever that is)
Step 4: Display = ABC x 80 + 1
Step 5: Display = (ABC x 80 + 1) x 250 = ABC x 20000 + 250
Step 6: Display = ABC x 20000 + 250 + DEFG
Step 7: Display = ABC x 20000 + 250 + DEFG x 2
Step 8: Display = ABC x 20000 + DEFG x 2
Step 9: Display = ABC x 10000 + DEFG = ABCDEFG.

Ta-da, the display reads your phone number, unless you live in a country where phone numbers have other than seven digits or -- weirder, somewhere where the first digit is allowed to be zero.

Here&#39;s one in a similar vein -- it&#39;s a little better concealed (I think). It works better if you tell it out loud to a friend and have them work through the calculations:

1. Reset your calculator so that the display = 0.
2. Enter the first three digits of your telephone number.
4. Multiply by 1875.
6. Multiply by 8.
8. Multiply by 2.
9. Add the last four digits of your telephone number. ("Oh, did I already tell you to do that? No, don&#39;t bother undoing it, the trick&#39;ll work anyway...")
10. Subtract ______(*)
11. Divide by 3.

(*) You know your friend&#39;s last name, so you multiply the number of letters in the name by 16, and then add 60,000 to that number. So, for example if your friend&#39;s last name was "Smith", you&#39;d tell your friend to subtract 60080.

#### yaoifun

##### Just Browsing
thats cool&#33; Math is quite possibly one of the wierdest, coolest, and most frustrating things ever&#33;

#### MASSIVEPKGO_CHUCK

##### Legendary Member
Interesting and very cool, it gave me my exact phone #.

#### D_Martin van Burden

##### Account Disabled
Originally posted by mindseye@Mar 25 2005, 01:58 PM
(*) You know your friend&#39;s last name...
[post=293969]Quoted post[/post]​

That&#39;s when the trick failed me. You say "your friend&#39;s last name." When I used MY last name both times (no, duh), it worked, but when I put in my friend&#39;s last name -- seven letters long -- it didn&#39;t work. Close result, but not quite my number.

#### mindseye

##### Experimental Member
Originally posted by DeeBlackthorne@Mar 26 2005, 01:53 PM
That&#39;s when the trick failed me. You say "your friend&#39;s last name." When I used MY last name both times (no, duh), it worked, but when I put in my friend&#39;s last name -- seven letters long -- it didn&#39;t work. Close result, but not quite my number.
[post=294196]Quoted post[/post]​

That&#39;s weird. Here&#39;s what I&#39;m getting at each step. Where do our results disagree?

Step 1: Display = 0
Step 2: Display = ABC
Step 3: Display = ABC + 2
Step 4: Display = (ABC x 1875) + 3750
Step 5: Display = (ABC x 1875) + 3757 (seven letters in the last name)
Step 6: Display = (ABC x 15000) + 30056
Step 7: Display = (ABC x 15000) + 30056 + DEFG
Step 8: Display = (ABC x 30000) + 60112 + (DEFG x 2)
Step 9: Display = (ABC x 30000) + 60112 + (DEFG x 3)
Step 10: "Subtract 60112." Display = (ABC x 30000) + (DEFG x 3)
Step 11: Display = ABC x 10000 + DEFG

#### D_Martin van Burden

##### Account Disabled
Step 5 says to add the letters in YOUR last name. Step 10 says "your friend&#39;s last name." It works fine if you use the same last name in both places, but not different last names -- mine vs. my friend&#39;s. Sorry I didn&#39;t make that more clear in the previous post.

#### mindseye

##### Experimental Member
Originally posted by DeeBlackthorne@Mar 26 2005, 03:33 PM
Step 5 says to add the letters in YOUR last name. Step 10 says "your friend&#39;s last name." It works fine if you use the same last name in both places, but not different last names -- mine vs. my friend&#39;s. Sorry I didn&#39;t make that more clear in the previous post.
[post=294221]Quoted post[/post]​

Ah. Got it. Well, like I said earlier, it works best if you read it out loud to a friend. In my mind, I was phrasing the steps to be read to someone else. Sorry to have been unclear on that point.

#### Kimahri

##### Cherished Member
Originally posted by Pecker@Mar 25 2005, 01:00 PM
It wouldn&#39;t give me the answer. I&#39;m unlisted.
[post=293942]Quoted post[/post]​

#### SomeGuyOverThere

##### Sexy Member
OFcourse that didnt work for me as I have a 6 digit phone number :/

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