Two identical tanks E and F contained some water. Tank E was ¹₆ filled and Tank F was ¹₇ filled. The ratio of the total mass of Tank E and the water in it to the total mass of Tank F and the water in it was 12 : 11. The total mass of the two tanks and the water they contained was 6670 g. What is the mass of an empty tank?
Mass of Tank E and the water inside = 12 u
Mass of Tank F 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 = 6670

1 u = 6670 ÷ 23 = 290

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

Fraction of the water that Tank E had more than Tank F 
= 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 290
= 1450 g

Answer(s): 1450 g