Two solid compounds X and Y dissociates at a certain temperature as follows 
 $$\begin{gathered} X\left(s\right)\rightleftharpoons A\left(g\right)+2B\left(g\right);K_{P_1}=9\times {10}^{-3}{\text{\hspace{0.17em}\hspace{0.17em}atm}}^3 \\ Y\left(s\right)\rightleftharpoons 2B\left(g\right)+C\left(g\right);K_{P_2}=4.5\times {10}^{-3}{\text{\hspace{0.17em}\hspace{0.17em}atm}}^3 \end{gathered}$$
 The total pressure of gases over a mixture of X and Y is P atmosphere then find the value of 4P? (Take nearest integer)

Let x is partial pressure of A and y is partial pressure of C when both equilibrium simultaneously established in a vessel
  $$\begin{gathered} \begin{array}{l}X\left(s\right)\rightleftharpoons \underset{x}{A\left(g\right)}+\underset{(2x+2y);}{2B\left(g\right)}\\ K_{P_1}=P_A.P_B^2\left(\text{total}\right)\end{array} \\ \begin{array}{l}Y\left(s\right)\rightleftharpoons \underset{x}{C\left(g\right)}+\underset{(2y+2x);}{2B\left(g\right)}\\ K_{P_2}=P_C.P_{B\left(\text{total}\right)}^2\end{array} \end{gathered}$$
  $$\begin{gathered} \frac{{\text{K}}_{\text{P1}}}{{\text{K}}_{\text{P2}}}\text{=}\frac{\text{x}}{\text{y}}\Rightarrow \text{x=2y} \\ {K}_{P1}=x{(2x+2y)}^2 \\ \Rightarrow x=0.1atm; \\ \therefore y=0.05atm \end{gathered}$$
   Total pressure of gases  ${\text{=P}}_{\text{A}}{\text{+P}}_{\text{B}}{\text{+P}}_{\text{C}}$
  $$\begin{gathered} \text{=3}(x+y) \\ \text{=0.45\hspace{0.17em}atm.} \end{gathered}$$