"calculate the volume, in ml. of the 1.0 m naoh stock solution needed to prepare 250 ml of 0.1 molar naoh."

A molar unit will be equal to moles of solute per 1 liter of solvent. Then, in 1 M NaOH solution, there will be 1 moles NaOH for every 1-liter solution. To answer this question, you need to know how many moles of NaOH you need for 250ml of 0.1 M NaOH. The same amount of molecule will be needed to ake the solution. The formula would be:

molar concentration = moles of molecule / liters of solvent
moles of molecule = molar concentration / liters of solvent

moles of molecule1 =moles of molecule2
1M * X = 0.1 M * (250/1000ml)
X= 0.1 M / 1M * (1/4)
X= (1/10) * (1/4)= 1/40 liters= 25ml

It is a product

Hi + naoh -> h2o + nal