A few math tricks

Here's a sneaky way to find out someone's age who won't tell you:

Ask the person to multiply the first number of his or her age by 5
Tell them to add 3
Now tell them to double this figure
Have the person add the second number of his or her age to the figure and have them tell you their answer
Deduct 6 and you will have their age!

Here is another

Tell someone to secretly input their age into a calculator and multiply it by 3367.
Now, tell them to multiply it by 3.
Next, tell them to write down their answer on a piece of paper and to clear all the information on the calculator so far.
Now, use that number on the piece of paper and divide it by 10101.
RESULT: The person's age!

The reason this trick works because 10101 is equal to 3367*3. And multiplying any two-digit number by 10101 is the same as writing it three times (e.g. 282828). Thus, when a number is multiplied by 3367, then by 3, it is really being multiplied by 10101. And of course, when you divide it by 10101 at the end of the trick, you get your original number, in this case your age.

And here is another

Magic Addition Trick #1
Amaze the peons with this one. It's simple. It's effective. It gets them every time.
Ask your mark to pick three (3) different numbers between 1 and 9.
Tell him or her (or her or him) to write the three numbers down next to each other, largest first and smallest last, to form a single 3-digit number. Tell him/her not to tell you what the numbers are.
Next have her or him form a new 3-digit number by reversing the digits, putting the smallest first and the largest last. And write this number right underneath the first number.
Now have him or her subtract the lower (and smaller) 3-digit number from the upper (and larger) 3-digit number. Tell them not to tell you what the result is.
Now you have a choice of wrap-ups:
Ask your friend to add up the three digits of the number that results from subtracting the smaller from the larger 3-digit number. Then amaze him or her by teling them what the sum of those three numbers is. The sum of the three digit answer will always be 18!
Tell your friend that if she or he will tell you what the first OR last digit of the answer is, you will tell her or him what the other two digits are. This is possible because the middle digit will always be 9, and the other two digits will always sum to 9! So to get the digit other than the middle one (which is 9) and other than the digit that your friend tells you, just subtract the digit your friend tells you from 9, and that is the unknown digit.