You know that "magic" thing people do, when they ask you to pick a number, subtract something, divide by something, blah blah blah, and in the end they guess your number? I've been trying to figure out how to do it since fourth grade, and I still can't understand it. I'm going into my sophomore year, and I've decided that it's time I can do this thing. Can someone please explain to me how this works? I can't figure it out!
James Ernst
Favorite Answer
There are a great many ways to perform this trick. Generally, there are two basic methods.
1) Send you through calculations which end up cancelling out the original selection, and forcing your result to be a specific value. "Is your final result 7?"
2) Send you through calculations which seem complicated, but can easily be reversed. For example, you give them a number, and they divide it by 12 to get your starting value.
What is the set of calculations to which you are referring?
mouska7
Imagine that your target picks the number "x". Your job is to figure it out. Basically, what you want your target to do it to tell you his number without him knowing he did. So you trick him by adding, subtracting, etc. numbers from x to confuse him.
Take this as an example:
You want to know someones age: let's say they are 25 years old, so their age is 10x + y, where x = 2 and y = 5.
1) Multiply the first number of your age by 5: 5x
2) Add three: 5x + 3
3) Double this figure: 2(5x + 3) = 10x + 6
4) Add the second number of the persons age to the total: 10x + y + 6
5) Subtract 6 and get their age: 10x + y
Pretty easy once you see how it works.
MathsTutor
Example:
"Think of a number, multiply it by 2, add 14, divide by 2, take away the number you first thought of. The answer is 7."
(((n*2)+14)/2)-n
=((n*2)/2+14/2)-n
=(n+7)-n
=(7+n)-n
=7
The series of calculations the volunteer is asked to perform are carefully contrived so that the end result is always the same, as shown by the algebra above. There must always be at least one reference to 'the number you first thought of' (n).
There are variants of the trick, such as the one above, which I have never heard before. So thanks for that!
Anonymous
1. think of a two digit number. (example 23) 2. add up the two digits (2 + 3 = 5) 3. subtract that number from your original number (23 - 5) 4. your answer will always be a multiple of 9 best answer plz
mamo
i'm going to post that on my next post in my blog.
find math tricks else here:
mathorhealth.blogspot.com