Given :
Commercial hydrochloric acid is 12.1 M.
To Find :
Volume of commercial HCl solution should be used to prepare 250.0 mL of 3.00 M HCl.
Solution :
We know :
[tex]M_1V_1=M_2V_2\\\\V_1=\dfrac{M_2V_2}{M_1}\\\\V_1=\dfrac{3\times 250}{12.1}\ mL\\\\V_1=61.98\ mL[/tex]
Therefore, volume of commercial HCl required is 61.98 mL.
Hence, this is the required solution.