Magic Math...How's it work?

[Blue70]

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?

[GT350Clone]

How It Works

Step 2 asks you to write a number. This will be different for each person, so we will call it x.
Step 3 says to multiply this number by 80. So we now have 80x.
Step 4 says to add one. This gives us 80x+1.
Step 5 tells us to multiply by 250. This gives 250(80x+1), which multiplies to 20,000x+250.
Step 6 has us add the last four digits of the phone number. This four digit number will be different for each person, so we will call this one y. So our total number now looks like 20,000x+250+y.
Step 7 says to add this same number again, giving us 20,000x+250+2y.
Step 8 has us subtract 250. So we are now looking at
20,000x+250+2y-250 = 20,000x+2y.
Step 9 tells us to finally divide by two. Now (20,000x+2y)/2 gives us 10,000x+y. Multiplying x by 10,000 moves the three numbers stored in x to the left of four zeros, and adding the four digits stored in y, replaces the zeros and gives you your phone number.

[Jagarang]

Great breakdown 350!! Cool! I need to go back to Algebra 101

[LowBuckX]

How It Works

Step 2 asks you to write a number. This will be different for each person, so we will call it x.
Step 3 says to multiply this number by 80. So we now have 80x.
Step 4 says to add one. This gives us 80x+1.
Step 5 tells us to multiply by 250. This gives 250(80x+1), which multiplies to 20,000x+250.
Step 6 has us add the last four digits of the phone number. This four digit number will be different for each person, so we will call this one y. So our total number now looks like 20,000x+250+y.
Step 7 says to add this same number again, giving us 20,000x+250+2y.
Step 8 has us subtract 250. So we are now looking at
20,000x+250+2y-250 = 20,000x+2y.
Step 9 tells us to finally divide by two. Now (20,000x+2y)/2 gives us 10,000x+y. Multiplying x by 10,000 moves the three numbers stored in x to the left of four zeros, and adding the four digits stored in y, replaces the zeros and gives you your phone number.

Thanks now my brain is ooozing from my ears