( 1 - 1/99) x ( 1 - 1/100) x...(1 - 1/2006)

* Hướng dẫn giải

$1-\frac{1}{99} x 1 - \frac{1}{100}....1-\frac{1}{2006}$
=($\frac{99}{99}-\frac{1}{99}$)x($\frac{100}{100}-\frac{1}{100}$)....($\frac{2006}{2006}-\frac{1}{2006}$) = $\frac{98}{99}x\frac{99}{100}....\frac{2005}{2006}=\frac{98}{2006}$