OT - math teaser

A

A*80

A*80+1

(A*80+1)*250 = A*20000 + 250

A*20000 + 250 + 2B

= A*20000 + 2B

= A*10000 + B

Hey, it's my phone number (base 10000)! YMMV if not in the US.

Dang, it's my girlfriend's number!

I note that step 3 and step 7 cancel each other and have no effect but to cause confusion.

In step 2 and step 4 you are multiplying your prefix by 20,000, but in step

8 you cut it back in half so in effect all you are doing is to add four zeros to your prefix.

The suffix is then added in twice, but again step 8 cuts it back to it's original form.

This is kind of like taking a three digit number such as 123 and appending it to itself to give you 123,123 and then observing that in cases where you do this the number will be evenly divisible by 7 and 11.

The reason it works that way is because you are in effect multiplying the original 3 digit number by 1001, and since 1001 is divisible by both 7 and

11 anything you multiply to 1001 will also be divisible by both 7 and 11.

1) A 2) 80A 3) 80A +1 4) 250 [ 80A+1] 5) 250 [ 80A+1]+ B 6) 250 [ 80A+1] + 2B 7) 250 [ 80A+1] + 2B -250 8) [250 [ 80A+1] + 2B -250] /2 = 125 80 A + 125 + 250B - 125 = 10000A + B

Ya, It's what I owe the IRS. :(