I will guess your age (using a math trick) #1
There are lots of number tricks you can do by using math. You can give someone a particular set of instructions and calculations and their current age can be deduced. To them it appears as though you are performing a magic trick, but all you need to know are the instructions. The math will work every time. Another set of instructions can be given to get the month and day of their birth. You can also use math to appear to guess the age of a stranger.
This is my second quiz! Use a calculator to follow the instruction! Press the equal sign after every instruction! It is impossible for the math trick to fail if it does maybe you calculate it wrong!