Answer:B

Feedback:20 buckets of water fill a tank when the capacity of each bucket is 18 litres.

∴ Capacity of the tank = 20 × 18 = 360 litres

∵ in the second case, Capacity of each bucket = 9 litres

Number of buckets needed = Total capacity of the tank/capacity of one bucket

∴ No. of buckets required = 360/ 9 = 40

Thus, 40 buckets are needed to fill the tank, if the capacity of each bucket is 9 litres.