The figure is not drawn to scale. Y and Z are two containers. The base area of Y is 11 cm² while the base area of Z is 50 cm². Container Y and Z contained some water and the height of the water level in Container Y was 55 cm as shown. Dan then poured some water from Container Y into Container Z. After that, the height of the water level in both tanks became 25 cm. What was the height of the water level in Container Z at first?
Change in the water level of Container Y
= 55 - 25
= 30 cm

Volume of water poured in the Container Z
= 11 x 30
= 330 cm³ 

Height increase in Container Z
= 330 ÷ 50
= 6.6 cm

Original height of the water in Container Z
= 25 - 6.6
= 18.4 cm

Answer(s): 18.4 cm