Question

If 125 mL of a 6.00 M KNO3 solution is diluted with 100.0 mL of water, the molarity of the resulting solution would be

Answer 1

ASSUMING volumes are additive, which isn't exactly so, it will be
6.00M x (125/225) = ?

or use the dilution formula
mL1 x M1 = mL2 x M2
100*6.00 = 225*M2.
Solve for M2.

Answer 2

3.33 M