1. **State the problem:** We want to find the mass of one nickel given the total mass for different numbers of nickels. 2. **Identify the relationship:** The total mass is proportional to the number of nickels. We can use the formula: $$\text{Total mass} = \text{Number of nickels} \times \text{Mass per nickel}$$ 3. **Use the data to find the mass per nickel:** Using the first data point (40 nickels, 200 grams): $$200 = 40 \times \text{Mass per nickel}$$ 4. **Solve for mass per nickel:** $$\text{Mass per nickel} = \frac{200}{40}$$ $$\text{Mass per nickel} = 5 \text{ grams}$$ 5. **Verify with other data points:** For 50 nickels: $$250 = 50 \times 5$$ For 60 nickels: $$300 = 60 \times 5$$ Both check out correctly. **Final answer:** The mass of one nickel is **5 grams**.