Figure R shows a closed rectangular tank of dimensions 40 cm by 40 cm by 70 cm with a cube of edge 16 cm glued to its bottom right corner. The tank contains 85 litres of water. Figure S 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 S 
= 40 - 16
= 24 cm

Volume of water under the cube in Figure S 
= 70 x 40 x 24
= 67200 cm³ 

1 ℓ = 1000 
85 ℓ = 85000cm³ 

Volume of water beside the cube
= 85000 - 67200
= 17800 cm³ 

Base area of water beside the cube
= (40 x 70) - (16 x 16)
= 2800 - 256
= 2544 cm² 

Height of water level beside the cube
= 17800 ÷ 2544
≈ 7.00 cm

Height of the water level
= 7.00 + 16
≈ 23 cm

Answer(s): 23 cm