A hardware salesman measures the mass of a box containing 1000 washers. The mass is $0.3588 \mathrm{~kg}$. What is the mass of a single washer in milligrams? Write your answer as a decimal. Explanation Check

Step 1 ：Convert the mass from kilograms to milligrams using the conversion factor 1 kg = 1,000,000 mg. So, \(0.3588 \text{ kg} = 0.3588 \times 1,000,000 \text{ mg} = 358,800 \text{ mg}\).

Step 2 ：Divide the total mass by the number of washers to find the mass of a single washer: \(\frac{358,800 \text{ mg}}{1000 \text{ washers}} = 358.8 \text{ mg/washer}\).

Step 3 ：\(\boxed{358.8 \text{ mg/washer}}\) is the mass of a single washer.