$\text{A=(1-$\dfrac{1}{2}$)×(1- $\dfrac{1}{3}$)×......×(1- $\dfrac{1}{9}$)}$
$\text{A=$\dfrac{1}{2}$×$\dfrac{2}{3}$×.....× $\dfrac{8}{9}$}$
$\text{A=$\dfrac{1×2×....×8}{2×3×....×9}$}$
$\text{⇒A=$\dfrac{1×(2×....×8)}{(2×3×....×8)×9}$}$
$\text{⇒A=$\dfrac{1}{9}$}$
$\text{Vì $\dfrac{1}{9}$ <1}$
$⇒A<1$