Two identical tanks K and L contained some water. Tank K was ¹₂ filled and Tank L was ¹₃ filled. The ratio of the total mass of Tank K and the water in it to the total mass of Tank L and the water in it was 6 : 5. The total mass of the two tanks and the water they contained was 1870 g. What is the mass of an empty tank?
Mass of Tank K and the water inside = 6 u
Mass of Tank L and the water inside = 5 u

Total mass of the two tanks and the water inside them
= 6 u + 5 u
= 11 u

11 u = 1870

1 u = 1870 ÷ 11 = 170

Mass of Tank K and the water in it more than mass of Tank L and the water in it 
= 6 u - 5 u
= 1 u

Fraction of the water that Tank K had more than Tank L 
= 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 tank
= 5 u - 2 u
= 3 u
= 3 x 170
= 510 g

Answer(s): 510 g