A hardware salesman measures the mass of a box containing

1000

washers. The mass is

0.4168

kg

. What is the mass of a single washer in milligrams? Write your answer as a decimal.

In this question, the box with 1000 washers has 0.4168kg mass. Then, to find the mass of a single washer you need to divide the mass with the number of washers. Then, you need to convert the unit into milligrams (1kg = 10^6mg)

It would be 0.4168 kg / 1000 * 10^6 milligram/kg = 4168mg.