Two identical pails A and B contained some water. Pail A was ¹₂ filled and Pail B was ¹₃ filled. The ratio of the total mass of Pail A and the water in it to the total mass of Pail B and the water in it was 8 : 7. The total mass of the two pails and the water they contained was 1950 g. What is the mass of an empty pail?
Mass of Pail A and the water inside = 8 u
Mass of Pail B and the water inside = 7 u

Total mass of the two pails and the water inside them
= 8 u + 7 u
= 15 u

15 u = 1950

1 u = 1950 ÷ 15 = 130

Mass of Pail A and the water in it more than mass of Pail B and the water in it 
= 8 u - 7 u
= 1 u

Fraction of the water that Pail A had more than Pail B 
= ¹₂ - ¹₃
= ³₆ - ²₆
= ¹₆ 

¹₆ of the water capacity → 1 u
²₆ of the water capacity → 2 x 1 u = 2 u

Mass of an empty pail
= 7 u - 2 u
= 5 u
= 5 x 130
= 650 g

Answer(s): 650 g