Cool math trick

[Renew Deal]

Here is a cool math trick about your phone number:

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

What number did you get?

[PVnRT]

1. Gotta have something to do with adding that 1

Too bad I didn't take a number theory class...

I get my phone numbers both times I tried it.

[Dufaeth]

5. not the 1

you can leave out the 1 and the subtracting 250 and it should still work. Tricks like these boil down to "multiply by 2, ok now divide by 2. Look! you get the same number!"

[catzies]

2. OMG it works.

That's pretty cool.

[burythehatchet]

3. Hey I got YOUR phone number

[TlalocW]

4. If you break down the formula

It comes down to 10,000 X + Y where X is the first 3 digits of your phone number, and Y is the last four digits. Multiplying say, 555 by 10,000 gives you 5,550,000. Adding the last four digits - say 1212 then gives you 5,551,212, which is your phone number.

The formula (after you go through all of the instructions) is:

{250(80(X) + 1) + 2Y - 250}/2 ->
{20,000X + 250 + 2Y - 250}/2 ->
{20,000X + 2Y}/2 ->
10,000X + Y

TlalocW

[Scottie72]

13. Darn you beat me to it!

I had basically the same post to give right here on piece of scrap paper!

Not all that amazing once you see how it works.

[VOX]

6. Cool! Good thing I knew my phone number, so I could, uh...

Know my phone number.

Nifty trick, Bleachers7 -- thanks for posting!

:toast:

[SCDem]

7. Hey that is pretty cool

[Kamika]

8. I did it in my head

It didn't work though.. got a completely different nr then my phone

[burythehatchet]

12. Kamika - do you need your head examined?

;)

[TXlib]

9. Here's why it works

1. Grab a calculator. (you won't be able to do this one in your head)

OK

2. Key in the first three digits of your phone number (NOT the area code)

x

3. Multiply by 80

80x

4. Add 1

80x + 1

5. Multiply by 250

250(80x + 1) = 20000x + 250

6. Add the last 4 digits of your phone number

20000x + 250 + y

7. Add the last 4 digits of your phone number again.

20000x + 250 + 2y

8. Subtract 250

20000x + 2y

9. Divide number by 2

10000x + y

x is a 3-digit number, so 10000x has the form XXX0000.
y is a 4-digit number, so adding it to XXX0000 gives XXXYYYY, which is your phone number.

[ALago1]

10. Ooh nice work

Some smart peoples around these parts...:D

[Drifter]

11. Here try this one ...

Take your favorite Number
Add 1
Subtract 1
The resulting number should be your favorite number.
Amazing isn't it.


If you can come up with one of these that does not include entering all of the information that it claims to provide ... then I'll be impressed.

Cheers
Drifter