The figure shows a tank made up of 3 sections. Cuboid J with a square base of side 4 cm and height 27 cm. Cube K with a side of 15 cm. Cuboid L that is 61 cm by 25 cm by 47 cm. Water from a tap above flows down at a rate of 2.8 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 K
= 15 x 15 x 15
= 3375 cm³ 

Volume of L
= 61 x 25 x 47
= 71675 cm³ 

2 ℓ = 2000 cm³ 
2.8 ℓ = 2800 cm³ 

Net increase in volume per minute
= 2800 - 2000
= 800 cm³/min

Height of J to be filled with water
= 70 - (47 + 15)
= 8 cm

Volume of water in J
= 4 x 4 x 8
= 128 cm³ 

Volume of water in L, K and part of J
= 71675 + 3375 + 128
= 75178 cm³ 

Time taken to reach height
= 75178 ÷ 800
≈ 94 min (Correct to nearest whole number)

Answer(s): 94 min