Figure Z shows a closed rectangular tank of dimensions 40 cm by 40 cm by 90 cm with a cube of edge 20 cm glued to its bottom right corner. The tank contains 85 litres of water. Figure A 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 A 
= 40 - 20
= 20 cm

Volume of water under the cube in Figure A 
= 90 x 40 x 20
= 72000 cm³ 

1 ℓ = 1000 
85 ℓ = 85000cm³ 

Volume of water beside the cube
= 85000 - 72000
= 13000 cm³ 

Base area of water beside the cube
= (40 x 90) - (20 x 20)
= 3600 - 400
= 3200 cm² 

Height of water level beside the cube
= 13000 ÷ 3200
≈ 4.06 cm

Height of the water level
= 4.06 + 20
≈ 24.06 cm

Answer(s): 24.06 cm