Two identical containers B and C contained some water. Container B was ¹₆ filled and Container C was ¹₇ filled. The ratio of the total mass of Container B and the water in it to the total mass of Container C and the water in it was 12 : 11. The total mass of the two containers and the water they contained was 3220 g. What is the mass of an empty container?
Mass of Container B and the water inside = 12 u
Mass of Container C 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 = 3220

1 u = 3220 ÷ 23 = 140

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

Fraction of the water that Container B had more than Container C 
= ¹₆ - ¹₇
= ⁷₄₂ - ⁶₄₂
= ¹₄₂ 

¹₄₂ of the water capacity → 1 u
⁶₄₂ of the water capacity → 6 x 1 u = 6 u

Mass of an empty container
= 11 u - 6 u
= 5 u
= 5 x 140
= 700 g

Answer(s): 700 g