At least 125.0 milliliters of a 6.0 M NaOH solution is needed to prepare 250.0 milliliters of a 3.0 M NaOH solution.
The concentration of the 6.0 M NaOH is double that of the 3.0 M NaOH, so you need half as much of the 3.0 M NaOH volume of 6.0 M NaOH in order to prepare the 3.0 M NaOH with 6.0 M NaOH.
