1. **Problem:** Find the molarity of a solution using 550 mL and 250 moles of sodium chloride. 2. **Formula:** Molarity ($M$) is defined as moles of solute divided by liters of solution: $$M = \frac{\text{moles}}{\text{liters}}$$ 3. **Convert volume to liters:** Since 1 L = 1000 mL, convert 550 mL to liters: $$550\ \text{mL} = \frac{550}{1000} = 0.55\ \text{L}$$ 4. **Calculate molarity:** Substitute moles = 250 and volume = 0.55 L into the formula: $$M = \frac{250}{0.55}$$ 5. **Simplify:** $$M = \frac{250}{0.55} = 454.545...$$ 6. **Final answer:** The molarity of the solution is approximately $$\boxed{454.55\ \text{M}}$$