Guess...Birth day......!!!!!!

Here's a fun trick to show a friend, a group, or an entire class of people. I have Seen this fun, mathematical trick in one of the blog...that seems good..so i posted to my blog...for all of us.
Let's Try how it works...(but it has some calculations better use calculaor...:-)
Tell the person (or class) to think of their birthday...and that you are going to guess it.
Follow these steps....

Step 1) Have them take the month number from their birthday: January = 1, Feb = 2 etc.

Step 2) Multiply that by 5

Step 3) Then add 6

Step4) Then multiply that total by four

Step5) Then add 9

Step 6) Then multiply this total by 5 once again

Step 7) Finally, have them add to that total the day they were born on. If they were born on the 18th, they add 18, etc.
Have them give you the total. In your head, subtract 165, and you will have the month and day they were born on!

How It Works :
Let M be the month number and D will be the day number.
After the seven steps the expression for their calculation is:
5 (4 (5 M + 6 ) + 9 ) + D = 100 M + D + 165
Thus, if you subtract off the 165,
what will remain will be the month in hundreds plus the day!