Two identical containers J and K contained some water. Container J was ¹₈ filled and Container K was ¹₉ filled. The ratio of the total mass of Container J and the water in it to the total mass of Container K and the water in it was 12 : 11. The total mass of the two containers and the water they contained was 4600 g. What is the mass of an empty container?
Mass of Container J and the water inside = 12 u
Mass of Container K and the water inside = 11 u

Total mass of the two containers and the water inside them
= 12 u + 11 u
= 23 u

23 u = 4600

1 u = 4600 ÷ 23 = 200

Mass of Container J and the water in it more than mass of Container K and the water in it 
= 12 u - 11 u
= 1 u

Fraction of the water that Container J had more than Container K 
= ¹₈ - ¹₉
= ⁹₇₂ - ⁸₇₂
= ¹₇₂ 

¹₇₂ of the water capacity → 1 u
⁸₇₂ of the water capacity → 8 x 1 u = 8 u

Mass of an empty container
= 11 u - 8 u
= 3 u
= 3 x 200
= 600 g

Answer(s): 600 g