100 mL of a 0.1 M HCl solution, 200 mL of a 0.2 M HCl solution, 300 mL of a 0.3 M HCl solution, 400 mL of a 0.4 M HCl solution and 500 mL of a 0.5 M HCl solution are mixed. 200 mL of this solution is diluted with 300 mL of water. What is the molarity of HCl in the resultant solution?

The correct option is A 0.147 M
Molarity of the solution when all the given solutions are mixed
$=\frac{(100\times 0.1)+(200\times 0.2)+(300\times 0.3)+(400\times 0.4)+(500\times 0.5)}{1500}$
= $\frac{550}{1500}$ M
Now, 200 mL of this solution is diluted to 500 mL by adding 300 mL of water.
$M_i{V}_i=M_f{V}_f$
Where $M_i$ is the molarity of the initial solution and $M_f$ is the molarity of the solution after dilution and $V_i$ and $V_f$ are their respective volumes.
$\frac{550}{1500}\times 200=M_f\times 500$
$M_f=0.147$ M