This one is a relatively easy one and something that can be attempted by folks of all age groups. I picked it up on the internet from the following site: http://www.puzzles2puzzleu.com/
You have four 9’s and you may use any of the (+, -, /, *,.) as many times as you like.
Can you make an expression which gives a result of 100 by using four 9s and any arithmetic operators? If yes how many such expressions can you make?
As always, please send your answers to alokgoyal_2001@yahoo.com and if you like the puzzle, please share it with others.
Happy number crunching!
Alok Goyal's Puzzles Page 
Hi Alok,
This is Bala, your ex-colleague from SAP.
Nice puzzles :-). I got at least one way to achieve 100 = 99 + 9 / 9.
Regards,
Bala
9731722556.