Math Minds tell me how this works...

[irish]

HERE IS A MATH TRICK SO UNBELIEVABLE THAT IT WILL STUMP YOU. PERSONALLY, I WOULD LIKE TO KNOW WHO CAME UP WITH THIS.

 

1. GRAB A CALCULATOR---NOT AN ADDING MACHINE. (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?

 

And no it has nothing to do with Pi. At least I think.

Edited March 31, 2007 by irish

[CaP'N GRuNGe]

nifty

[Big John]

Steps 4 and 8 cancel each other out. (+1x250 then -250) This is the key and hides the process.

 

Steps 3 and 5 multiplies phone# by 20000 which ends in the 0000. (The added 1x250 hides this fact.)

 

Adding the last 4 digits twice adds twice this set. Then dividing by 2 gives back the last digits, and the placement of the 80x250 (20000) gives the place of the first 3 digits.

[jaxfactor]

Steps 4 and 8 cancel each other out. (+1x250 then -250) This is the key and hides the process.

 

Steps 3 and 5 multiplies phone# by 20000 which ends in the 0000. (The added 1x250 hides this fact.)

 

Adding the last 4 digits twice adds twice this set. Then dividing by 2 gives back the last digits, and the placement of the 80x250 (20000) gives the place of the first 3 digits.

 

 

Did you forget something Big John? Maybe ?

[Easy n Dirty]

Steps 4 and 8 cancel each other out. (+1x250 then -250) This is the key and hides the process.

 

Steps 3 and 5 multiplies phone# by 20000 which ends in the 0000. (The added 1x250 hides this fact.)

 

Adding the last 4 digits twice adds twice this set. Then dividing by 2 gives back the last digits, and the placement of the 80x250 (20000) gives the place of the first 3 digits.

 

Very nice.

 

Effectively, multiplying by 20,000 and later dividing by 2 is same as multiplying by 10,000, which gets the first 3 digits of the phone # 4 places to the left. You then fill in the 4 open places with the last 4 digits (by adding those 4 digits twice in steps 6 and 7 and then dividing that piece by 2 also).

[TheGrunt]

Steps 4 and 8 cancel each other out. (+1x250 then -250) This is the key and hides the process.

 

Steps 3 and 5 multiplies phone# by 20000 which ends in the 0000. (The added 1x250 hides this fact.)

 

Adding the last 4 digits twice adds twice this set. Then dividing by 2 gives back the last digits, and the placement of the 80x250 (20000) gives the place of the first 3 digits.