The figure is not drawn to scale. C and D are two containers. The base area of C is 39 cm² while the base area of D is 68 cm². Container C and D contained some water and the height of the water level in Container C was 40 cm as shown. Dan then poured some water from Container C into Container D. After that, the height of the water level in both tanks became 23 cm. What was the height of the water level in Container D at first?
Change in the water level of Container C
= 40 - 23
= 17 cm

Volume of water poured in the Container D
= 39 x 17
= 663 cm³ 

Height increase in Container D
= 663 ÷ 68
= 9.75 cm

Original height of the water in Container D
= 23 - 9.75
= 13.25 cm

Answer(s): 13.25 cm