# Thread: Math Trick (IF YOU SOLVE YOU GET A PRIZE!!!!)

1. ## Math Trick (IF YOU SOLVE YOU GET A PRIZE!!!!)

Alright, my teacher uses 5 pieces of paper. Each paper contains numbers on them, quite a few out of order numbers to 31 days on each card. She told me to look at the five papers and out of 5 of them my birthday number was in like 2 of them. after I told her which 2 and without looking at the cards she told me my birth date. She got it right. for example im born may 29th, she just told me i was born on the 29th. i was wondering how she did that...
She giving me extra credit which i need really badly cause i suck at math.

Winner with the best explanation and right answer to help me get the extra credit wins a prize

2. What's the prize?

3. lets just say its worth it and alot of kids on the site will get some lifetime "excitement"

4. A) She's a hacker. /report
B) She's a magician.

5. my teacher taught me this once let me try to remember

6. The short answer is that the numbers are not written on the cards randomly, but in a very specific pattern, so that someone who knows the trick can immediately tell you when your birthday is from the cards that have your birthday written on them. But you probably already guessed that much.

The long answer requires you to know a bit about binary numbers. Binary numbers use just two digits, 0 and 1. Like computers. In decimal numbers you write the number 425, and you know from the position of the numbers that it is 4 hundred plus 2 times 10 plus 5. Each position further to the left is ten times greater.

In binary numbers it's the same way, except you start with 1, and each position further to the left is just two times greater. So the number 11011 is 1 plus 1 times two plus 0 times four plus 1 time 8 plus 1 times 16.

So the numbers from 1 through 31 can be represented with five binary digits, because 31 equals 1 + 2 + 4 + 8 + 16, or 11111.

So you take your five pieces of paper, and you write on the first one all of the numbers from 1 through 31 that require ----1 in binary. (This happens to be all odd numbers from 1 through 31.) On the second paper you write all of the numbers that require ---1- in binary (2, 3, 6, 7, 10, and so on). Continue like that for all five pieces of paper.

If you want to be tricky, mix up the numbers on each piece of paper so that people can't spot a pattern. (This might make them look random, even though they're not.)

Your birthday, the 10th, is 2 plus 8, or 01010 in binary, so it would appear on the second and the fourth piece of paper, but not on any of the other three. All you teacher now has to do is convert 01010 to decimal: 2 + 8 = 10.
here you go
my prize?

7. Kable got it!

8. @KABLE
its not age its the day you were born like 1-31 days of the month the site u gave me is for age

The short answer is that the numbers are not written on the cards randomly, but in a very specific pattern, so that someone who knows the trick can immediately tell you when your birthday is from the cards that have your birthday written on them. But you probably already guessed that much.

The long answer requires you to know a bit about binary numbers. Binary numbers use just two digits, 0 and 1. Like computers. In decimal numbers you write the number 425, and you know from the position of the numbers that it is 4 hundred plus 2 times 10 plus 5. Each position further to the left is ten times greater.

In binary numbers it's the same way, except you start with 1, and each position further to the left is just two times greater. So the number 11011 is 1 plus 1 times two plus 0 times four plus 1 time 8 plus 1 times 16.

So the numbers from 1 through 31 can be represented with five binary digits, because 31 equals 1 + 2 + 4 + 8 + 16, or 11111.

So you take your five pieces of paper, and you write on the first one all of the numbers from 1 through 31 that require ----1 in binary. (This happens to be all odd numbers from 1 through 31.) On the second paper you write all of the numbers that require ---1- in binary (2, 3, 6, 7, 10, and so on). Continue like that for all five pieces of paper.

If you want to be tricky, mix up the numbers on each piece of paper so that people can't spot a pattern. (This might make them look random, even though they're not.)

Your birthday, the 10th, is 2 plus 8, or 01010 in binary, so it would appear on the second and the fourth piece of paper, but not on any of the other three. All you teacher now has to do is convert 01010 to decimal: 2 + 8 = 10.
here you go
my prize?
You got that off yahoo answers and I dont think its right becuase for it to be binary the teacher has to look at the card which she didnt...

9. Originally Posted by dw3fan
@KABLE
its not age its the day you were born like 1-31 days of the month the site u gave me is for age
Simple bro; she has a grade report.