Amazing Math

[Pasukun]

You will need a calculator.

 

First, pick a phone number.. (home, work, friend, or any number)

 

Enter the first 3 nubmers. (734-XXXX)

 

Multiply it by 80.

 

Add 1.

 

Multiply it by 250.

 

Now add last 4 numbers. (XXX-2782)

 

Add last 4 numbers again.

 

Subtract 250.

 

Finally, divide it by 2.

 

What numbers do you see?

Edited November 14, 2005 by Pasukun

[TCH-Thomas]

It showed me a phone number, almost anyway. There was some numbers missing or incorrect, but maybe it only works for U.S numbers.

 

Also a note to everyone (even though I think everyone knows this): Do not publish your phone number here in the forum.

[abinidi]

Well, to be honest, it isn't all that amazing... in fact, there are numbers thrown in there just to make it seem more impressive than it is.

 

Let us consider an example case where a phone number is 123-4567.

 

Since the example has you input the two parts of the phone number separatley, we'll break them into two distinct numbers. We'll let a variable, x, represent the number 123, and we'll let a variable, y, represent 4567.

 

In order to express this mathmatically, you can't just say

 

>xy

because that means 'x multiplied by y'

 

So to express this mathmatically, we'll say it is

>10000x + y

because if you multiply x by 10,000, then add y, you get your phone number.

 

(See, because 10,000 multiplied by x is just x with four zeros after it; add the last four digits, and you have your phone number).

 

Ok. so we know that 10,000x + y gives us our phone number. So lets look at the math that we are told to do.

 

If you write out the equation given, you get the following:

 

>{ [ ( 80x + 1 )250 ] + [2y - 250] / 2} = 10,000x + y

 

If you simplify the left side of the equation by doing the multiplication on the top of the fraction, you get the following:

 

>[( 20,000x + 250 +2y - 250) / 2] = 10,000x+y

 

Notice that on the top of the left side you have a +250 and a -250. They cancel themselves out, so you are left with:

 

>[( 20,000x + 2y) / 2] = 10,000x + y

 

Simplify the left side further by dividing by 2, and what do you get?

 

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

 

...which we already established is your phone number.

 

Basically you can put any 3-digit number between 100 and 999 in for x, and you can put any 4-digit number between 1000 and 9999 in for y, and the equation will work.

 

It is really quite simple math. Anytime I see these mysterious number tricks where I'm supposed to enter in any random number and get an expected output, I always know that I can substitue variables to see how it is done. That is, after all, the whole point of a variable.

 

Hope I didn't ruin it for anybody

[wampthing]

There are three kinds of people in this world...

Those who can count, and those who can't.

[cajunman4life]

Actually wampthing, there are 10 kinds of people in this world... those who understand binary, and those who don't.

[Deverill]

I thought it was (in light of Abinidi's explanation)

There are 2x+y where x=1 and y=x-1 kinds of people in the world,

those who understand algebra and those who don't.

[abinidi]

TCH-Jim -- EXACTLY!

[TCH-Thomas]

Alge what?

[TCH-Rob]

I always thought it was that there are two kinds of people in this world, those that are wrong and me.