Wednesday, March 28, 2007
Math Trick
Here is a math trick so unbelievable that it will stump you.
- Grab a calculator. (You wont be able to do this in your head)
- Key in the first three digits of your phone number if ur phone number is7 digits or else take the first 4 digits of ur number if its 8 digits.(onlyland line no.) (NOT the area code)
- Multiply by 80
- Add 1
- Multiply by 250
- Add the last four numbers of your phone number
- Add the last four numbers of your phone number again
- Subtract 250
- Divide number by 2
Do you recognize the answer ?
Labels: math trick
Stumble It!1 Comments:
commented by 
Unknown, 8:07 AM
Unknown, 8:07 AM
Here's the breakdown for you:
Given a number of the format 'xyzabcd'
1. Original formula:
{[250((xyz*80)+1)+2abcd]-250}/2=xyzabcd
2. Factor out a 2:
2{[125((xyz*80)+1)+abcd]-125}/2=xyzabcd
3. Divide by 2:
[125((xyz*80)+1)+abcd]-125]=xyzabcd
4. Multiply the 125 through:
(xyz*10000)+125+abcd-125=xyzabcd
5. Add the +125 and the -125 together:
(xyz*10000)+abcd=xyzabcd
That was a fun trick to work out. Nice work finding it! You can expand the trick by reserving the first four places of any integer greater than 9999 and using the rest in place of xyz. So even a full 10-digit phone number will work. So will an IP address...
To se the phone number 401.555.3838 simply separate out the last 4 digits and apply as normal.