Two identical pails E and F contained some water. Pail E was ¹₂ filled and Pail F was ¹₃ filled. The ratio of the total mass of Pail E and the water in it to the total mass of Pail F and the water in it was 5 : 4. The total mass of the two pails and the water they contained was 1080 g. What is the mass of an empty pail?
Mass of Pail E and the water inside = 5 u
Mass of Pail F and the water inside = 4 u

Total mass of the two pails and the water inside them
= 5 u + 4 u
= 9 u

9 u = 1080

1 u = 1080 ÷ 9 = 120

Mass of Pail E and the water in it more than mass of Pail F and the water in it 
= 5 u - 4 u
= 1 u

Fraction of the water that Pail E had more than Pail F 
= 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
= 4 u - 2 u
= 2 u
= 2 x 120
= 240 g

Answer(s): 240 g