Figure K shows a closed rectangular tank of dimensions 42 cm by 42 cm by 90 cm with a cube of edge 20 cm glued to its bottom right corner. The tank contains 90 litres of water. Figure L 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 L 
= 42 - 20
= 22 cm

Volume of water under the cube in Figure L 
= 90 x 42 x 22
= 83160 cm³ 

1 ℓ = 1000 
90 ℓ = 90000cm³ 

Volume of water beside the cube
= 90000 - 83160
= 6840 cm³ 

Base area of water beside the cube
= (42 x 90) - (20 x 20)
= 3780 - 400
= 3380 cm² 

Height of water level beside the cube
= 6840 ÷ 3380
≈ 2.02 cm

Height of the water level
= 2.02 + 20
≈ 22.02 cm

Answer(s): 22.02 cm