i need to know how to set up this problem for my finals, don't just post an answer please.

Question

How could you prepare 250mL of 0.20M NaCL using only a solution of 1.0M NaCL and water.

Answer 1

mL x M = mL x M.
250mL x 0.20 M = mL x 1.0 M
solve for mL of 1.0 M NaCl.
Then ? mL of 1.0 M NaCl in a 250 mL volumetric flask, and make to the mark with water.

Answer 2

another way to think on this is that you are diluting it by 5 times, so you need four parts water and one part concentrate.

1Part=50ml 1.0M NaCl
4 parts water: 200ml