math trick??

Question

How do people do that trick where you pick a number and multiply and divide it, and then at the end they guess the outcome number?

Answer 1

1) pick a number (best 1-10 because people can't add and multiply).
2) double it (multiply by two)
3) add some number (usually an even number 6, 10 ,20, etc)
4) divide it in half
5) Subtract the number you first started with.
6) answer is .......(always 1/2 of amount added).

Answer 2

they mentally work in reverse to get the answer
when they tell you to multiply by 5 they divide the answer you give them by 5, and when they tell you to add they subtract ad so on.

Here is an example:

pick a number (1-10) you pick [7]

multiply it by 3 you now have [21]

add 8 you now have [29]

what is the answer? you say 29

29 - 8 = 21/3 = your number was 7

Answer 3

It's very simple. The number u think was reduced in counting progress. Example:
U think a number
let +30
-15
- number u thinked
+10
finally x4
i'm sure that the result is 100
sorry about grammar. Have fun