A metre scale is balanced on a knife edge at its centre. When two coins, each of mass \( 10 \, \text{g} \) are put one on the top of the other at the \( 10.0 \, \text{cm} \) mark the scale is found to be balanced at \( 40.0 \, \text{cm} \) mark. The mass of the metre scale is found to be \( x \times 10^{-2} \, \text{kg} \). The value of \( x \) is __________.