--- >SUBJECT: MATH PROBLEM
>
>Here is a math trick so unbelievable 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'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 answer?

Readers have sent us explanations, which we post below:

assume
abc  = 3 first digits
defg = 4 last digits   step 1:       abc
step 2:  *     80
step 3:  +      1
step 4:  *    250
step 5:  +   defg
step 6:  +   defg
step 7:  -    250  
step 8:  /      2   step 6: Result = ((abc*80)+1)*250 + 2*defg
step 7: Result = ((abc*80)+1)*250 + 2*defg - 1*250
    <=> Result = ((abc*80)+1-1)*250 + 2*defg
    <=> Result = (abc*20000) + 2*defg
    <=> Result = 2*(abc*10000 + defg)
step 8: Result = 2*(abc*10000 + defg) / 2
    <=> Result = abc*10000 + defg   in a simpler way      abc
*  10000
=abc0000
+   defg
=abcdefg
The trick is to hide the fact that you multiply by 10000   ;-) Baltazar  

PS: It's college maths...

Quote of the day - on the Unbelievable Math Problem (Thanks Simon): Let x be the three digit number and let y be the four digit number... If you lay out the problem as it is worded with brackets etc, you'll end up with 10000x + y i.e. Your own phone number.... [Birdman comment: In the wee hours of the morning I usually have no inclination to fool around with these things, and anyway I can generally rely on somebody or another to proffer an answer. Another reader also gave his answer - see post.]

Second quote of the day (Another solution - Thanks Trent): Cool math problem - here's how it works: > x = first three digits of phone number y = last four digits of phone number > First step: 80*x Second step: 80x+1 Third step: 250*(80x+1) = 20000x + 250 Fourth step: 20000x + 250 + y Fifth step: 20000x + 250 + 2y Sixth step: 20000x + 2y Seventh step: [20000x + 2y]/2 = 10000x + y > The trick is moving the first 3 digits of your number by 4 decimal places which means multiplication by 10000. Easy enough. The last part is just the last 4 digit which occupy the thousands, hundreds, tens and ones places. Note you could have modified several of the steps but then it becomes obvious what is going on. [Birdman comment: If you haven't got it by now, you get an 'F' in Math Conspiracy Theory.]