Figure X shows a closed rectangular tank of dimensions 40 cm by 40 cm by 75 cm with a cube of edge 18 cm glued to its bottom right corner. The tank contains 85 litres of water. Figure Y shows the same rectangular tank lying on its side. Find the height of the water level, in centimetres, corrected to 2 decimal places.
Height of water under the cube in Figure Y 
= 40 - 18
= 22 cm

Volume of water under the cube in Figure Y 
= 75 x 40 x 22
= 66000 cm³ 

1 ℓ = 1000 
85 ℓ = 85000cm³ 

Volume of water beside the cube
= 85000 - 66000
= 19000 cm³ 

Base area of water beside the cube
= (40 x 75) - (18 x 18)
= 3000 - 324
= 2676 cm² 

Height of water level beside the cube
= 19000 ÷ 2676
≈ 7.10 cm

Height of the water level
= 7.10 + 18
≈ 25.1 cm

Answer(s): 25.1 cm