Two identical tanks B and C contained some water. Tank B was ¹₆ filled and Tank C was ¹₇ filled. The ratio of the total mass of Tank B and the water in it to the total mass of Tank C and the water in it was 12 : 11. The total mass of the two tanks and the water they contained was 4830 g. What is the mass of an empty tank?
Mass of Tank B and the water inside = 12 u
Mass of Tank C and the water inside = 11 u

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

23 u = 4830

1 u = 4830 ÷ 23 = 210

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

Fraction of the water that Tank B had more than Tank 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 tank
= 11 u - 6 u
= 5 u
= 5 x 210
= 1050 g

Answer(s): 1050 g