Cool math trick

[bigsteel15]

This is cool!
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?

[Tom Miller]

Just a slightly convoluted way of multiplying the first three digits of your phone number by 10,000 and then adding the last four digits.

Now, if the result was my social security number....

Regards,
Tom

[Deadhead]

It's just a neat manipulation of numbers.

Let x= first 3 digits
Let y= last 4 digits

The goal is to manipulate x and y so they equal 10,000x + y.

We could simply say "multiply the first 3 digits by 10,000 then add the last 4 digits", but that wouldn't be all that impressive.

So instead, they add things, multiply by things, subtract things, and divide by things.

The left side is the computation as you described it, the right side is what we'd like it to equal:
(((80x + 1) * 250) + 2y - 250) / 2 = 10,000x + y

Solving:
(20,000x + 250 + 2y - 250) / 2 = 10,000x + y

20,000x + 2y) / 2 = 10,000x + y

10,000x + y = 10,000x + y

[gsmittle]

It's just a neat manipulation of numbers.

Let x= first 3 digits
Let y= last 4 digits

The goal is to manipulate x and y so they equal 10,000x + y.

We could simply say "multiply the first 3 digits by 10,000 then add the last 4 digits", but that wouldn't be all that impressive.

So instead, they add things, multiply by things, subtract things, and divide by things.

The left side is the computation as you described it, the right side is what we'd like it to equal:
(((80x + 1) * 250) + 2y - 250) / 2 = 10,000x + y

Solving:
(20,000x + 250 + 2y - 250) / 2 = 10,000x + y

20,000x + 2y) / 2 = 10,000x + y

10,000x + y = 10,000x + y

Sorry, I lost you at "Let x=..."

Math makes my brain hurt.

g.

[Stytooner]

This one is easy. I didn't need no stinkin calculator. I know this answer by heart already.

[mater]

It's just a neat manipulation of numbers.

Let x= first 3 digits
Let y= last 4 digits

The goal is to manipulate x and y so they equal 10,000x + y.

We could simply say "multiply the first 3 digits by 10,000 then add the last 4 digits", but that wouldn't be all that impressive.

So instead, they add things, multiply by things, subtract things, and divide by things.

The left side is the computation as you described it, the right side is what we'd like it to equal:
(((80x + 1) * 250) + 2y - 250) / 2 = 10,000x + y

Solving:
(20,000x + 250 + 2y - 250) / 2 = 10,000x + y

20,000x + 2y) / 2 = 10,000x + y

10,000x + y = 10,000x + y

Sounds good to me.

[Lance]

Directions to the White House?

Yep, I figgered it out too. When do we all descend on that big house on Pennsylvania Ave. to start runnin' things??

[Deadhead]

I wish the tax code was that simple.

[venkatbo]

I wish the tax code was that simple.

Only wish that were true.... Say 10% of gross family/annual income...
Then a simple formulau: tax = 0.10 * income

Imagine all the savings in headaches, money, loss of tax-prep industry, IRS, and last but not the least paperwork (ie, trees - more wood for us :-)

Too many lobbies and revolving doors get affected... not possible :!)

/venkat

[stav]

If you can memorize the process, its a good way to get the phone number of a cute member of the opposite gender.