The figure shows a container made up of 3 sections. Cuboid K with a square base of side 4 cm and height 26 cm. Cube L with a side of 10 cm. Cuboid M that is 75 cm by 30 cm by 40 cm. Water from a tap above flows down at a rate of 3.4 litres per minute while water is drained out from the bottom at a rate of 2 litre per minute. How long did it take to fill up the container to a height of 60 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of L
= 10 x 10 x 10
= 1000 cm³ 

Volume of M
= 75 x 30 x 40
= 90000 cm³ 

2 ℓ = 2000 cm³ 
3.4 ℓ = 3400 cm³ 

Net increase in volume per minute
= 3400 - 2000
= 1400 cm³/min

Height of K to be filled with water
= 60 - (40 + 10)
= 10 cm

Volume of water in K
= 4 x 4 x 10
= 160 cm³ 

Volume of water in M, L and part of K
= 90000 + 1000 + 160
= 91160 cm³ 

Time taken to reach height
= 91160 ÷ 1400
≈ 65 min (Correct to nearest whole number)

Answer(s): 65 min