Math Trick: Reveal Common Answer with Few Steps

[anil]

any body know that trick where you tell the audience to pick a number and thell them to add a number and multiply by a number and then after a couple of sets everybody will have a common answer? If so could you please explain in detail regarding the procedure.

 

[e(ho0n3]

Check out this thread:
https://www.physicsforums.com/showthread.php?t=34283

 

[gazzo]

1) Pick a number between 1 and 10
2) multiply that number by 9
3) if the number is two digets, add the two digits together
4) subtract 5 from the answer.
5) if 1 = A, 2 = B, 3 = C, 4 = D, 5 = E, etc... think of a country with the letter your number represents.
5) Using the last letter of the country, think of an animal.

This is an example lol... steps 4 onwards aren't needed but amazingly, most people choose Denmark, and Kangaroo.

 

[fourier jr]

There are a bunch of those (3-4) in 'Mathematical Recreations and Essays' by Ball & Coxeter. That book is packed with all kinds of cool stuff.