A sample contains \( 10^{-2} \) \( \text{kg} \) each of two substances \( A \) and \( B \) with half lives \( 4 \, \text{s} \) and \( 8 \, \text{s} \) respectively. The ratio of their atomic weights is \( 1:2 \). The ratio of the amounts of \( A \) and \( B \) after \( 16 \, \text{s} \) is \( \dfrac{x}{100} \). The value of \( x \) is ________.
