More Math

[Aggie Hoopsfan]

Just for kicks.

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

Look familiar?

[travis2]

Just for kicks.

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

Look familiar?

Yeah, but can you write out the equation and show why it works? :p

[Aggie Hoopsfan]

Hey I'm not here to teach math, just with people's minds.

[travis2]

Hey I'm not here to teach math, just with people's minds.

And a good job you do.

[T Park]

in black magic.....

[baseline bum]

Assume your phone number is

x_6 x_5 x_4 - x_3 x_2 x_1 x_0

((x_6 * 10^2 + x_5 *10 + x_4) * 80 + 1) * 250 + 2 * (x_3 * 10^3 + x_2 *10^2 + x_1 *10 + x_0) - 250 ) / 2

= ( 20,000 (x_6 * 10^2 + x_5 *10 + x_4) + 250 + 2 * (x_3 * 10^3 + x_2 *10^2 + x_1 *10 + x_0) - 250) / 2

= ( 2 * 10,000 (x_6 * 10^2 + x_5 *10 + x_4) + 2 * (x_3 * 10^3 + x_2 *10^2 + x_1 * 10 + x_0 ) / 2
= 10,000 (x_6 * 10^2 + x_5 *10 + x_4) + (x_3 * 10^3 + x_2 *10^2 + x_1*10 + x_0)
= 10^4 (x_6 * 10^2 + x_5 *10 + x_4) + (x_3 * 10^3 + x_2 *10^2 + x_1*10 + x_0)
= (x_6 * 10^6 + x_5 *10^5 + x_4*10^4) + (x_3 * 10^3 + x_2 *10^2 + x_1*10 + x_0)
= x_6 * 10^6 + x_5 *10^5 + x_4*10^4 + x_3 * 10^3 + x_2 *10^2 + x_1*10 + x_0
, which is the base 10 representation of the phone number

x_6 x_5 x_4 - x_3 x_2 x_1 x_0

QED

Just for kicks.

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

Look familiar?

[bigzak25]

or basically that all that calculator translates to 10000 times the first 3 digits plus the last 4 digits....which is your phone number....