A village, having

Length of tank = l = 20 m

Breadth of tank = b = 15 m

Height of tank = h = 6 m

Volume of water in tank = volume of cuboidal tank

Volume of cuboid = lbh

⇒ volume of cuboidal tank = 20 × 15 × 6

= 1800 m³

1 m³ is 1000 litres

⇒ 1800 m³ = 1800 × 1000 = 1800000 litres

150 litres of water is required per head per day and the population of village is 4000

⇒ volume of water consumed by 4000 people per day = 4000 × 150 = 600000 litres

In one day village consumes 600000 litres of water

⇒ days require to consume 1800000 litres of water = = 3

Thus water of tank will last 3 days