Two identical containers S and T contained some water. Container S was ¹₉ filled and Container T was ¹₁₀ filled. The ratio of the total mass of Container S and the water in it to the total mass of Container T and the water in it was 13 : 12. The total mass of the two containers and the water they contained was 4000 g. What is the mass of an empty container?
Mass of Container S and the water inside = 13 u
Mass of Container T and the water inside = 12 u

Total mass of the two containers and the water inside them
= 13 u + 12 u
= 25 u

25 u = 4000

1 u = 4000 ÷ 25 = 160

Mass of Container S and the water in it more than mass of Container T and the water in it 
= 13 u - 12 u
= 1 u

Fraction of the water that Container S had more than Container T 
= ¹₉ - ¹₁₀
= ¹⁰₉₀ - ⁹₉₀
= ¹₉₀ 

¹₉₀ of the water capacity → 1 u
⁹₉₀ of the water capacity → 9 x 1 u = 9 u

Mass of an empty container
= 12 u - 9 u
= 3 u
= 3 x 160
= 480 g

Answer(s): 480 g