The figure shows a tank made up of 3 sections. Cuboid L with a square base of side 9 cm and height 27 cm. Cube M with a side of 15 cm. Cuboid N that is 67 cm by 18 cm by 40 cm. Water from a tap above flows down at a rate of 2.2 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 tank to a height of 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of M
= 15 x 15 x 15
= 3375 cm³ 

Volume of N
= 67 x 18 x 40
= 48240 cm³ 

2 ℓ = 2000 cm³ 
2.2 ℓ = 2200 cm³ 

Net increase in volume per minute
= 2200 - 2000
= 200 cm³/min

Height of L to be filled with water
= 70 - (40 + 15)
= 15 cm

Volume of water in L
= 9 x 9 x 15
= 1215 cm³ 

Volume of water in N, M and part of L
= 48240 + 3375 + 1215
= 52830 cm³ 

Time taken to reach height
= 52830 ÷ 200
≈ 264 min (Correct to nearest whole number)

Answer(s): 264 min