The figure shows a container made up of 3 sections. Cuboid L with a square base of side 9 cm and height 45 cm. Cube M with a side of 12 cm. Cuboid N that is 61 cm by 11 cm by 41 cm. Water from a tap above flows down at a rate of 3.7 litres per minute while water is drained out from the bottom at a rate of 1 litre per minute. How long did it take to fill up the container to a height of 64 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of M
= 12 x 12 x 12
= 1728 cm³ 

Volume of N
= 61 x 11 x 41
= 27511 cm³ 

1 ℓ = 1000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 1000
= 2700 cm³/min

Height of L to be filled with water
= 64 - (41 + 12)
= 11 cm

Volume of water in L
= 9 x 9 x 11
= 891 cm³ 

Volume of water in N, M and part of L
= 27511 + 1728 + 891
= 30130 cm³ 

Time taken to reach height
= 30130 ÷ 2700
≈ 11 min (Correct to nearest whole number)

Answer(s): 11 min