more math ques =)

heh...here's another math ques for u guys, think bout it :P

Just suppose that you have a large block of stone. While staring at this block of stone, it dawns on you that perhaps you should carve it into something. Luckily, you have a hammer and chisel handy.
But it's no ordinary hammer and chisel. Somehow, no matter how hard you hit the chisel, exactly one-half of one percent of the block chips off.
How many times do you have to hit the chisel before the block is less than half of its original size?

haha..have fun!! :b