The mass of a container is 5.81kg when completely filled with sugar. Its mass is 3.8kg when 3/8 of the sugar is removed. What is the mass of the container when it is empty?

When removing 3/8 of the sugar, you have 5,81 - 3,8 = 2,01 kg of sugar. To get the total amount of sugar you can do something like 2,01/3*8 = 5,36 kg of sugar. The mass of the container itself is therefore 5,81 - 5,36 = 0,45kg