Water flows into a tank at the rate of 40 ℓ per minute. After 25 min, the tap is turned off and the tank is 0.4 filled with water.

1. How much more water is needed to fill it to the brim?
2. The water in the tank is then poured into containers each 1.6 m long, 0.3 m wide and 25 cm high. What is the minimum number of containers needed?

(a)
0.4 =  ²₅

Let 5 u be the total volume of water when the tank is completely filled.

Volume of water in the tank
= 40 x 25
= 1000 ℓ

2 u = 1000

1 u = 1000 ÷ 2 = 500

Volume of water to fill the tank to the brim
= 5 u - 2 u
= 3 u
= 3 x 500
= 1500 ℓ

(b)
1 m = 100 cm
1.6 m = 160 cm
0.3 m = 30 cm

Volume of each container
= 160 x 30 x 25
= 120000 cm³

Volume of water in the tank = 1000 ℓ

1 ℓ = 1000 mℓ
1000 ℓ = 1000000 mℓ

Number of containers needed
= 1000000 ÷ 120000
= 8 r 40000

Minimum number of containers needed
= 8 + 1 
= 9

Answer(s): (a) 1500 ℓ; (b) 9