12 buckets of water fill a tank when the capacity of each bucket is 13.5 litres. How many buckets will be needed to fill the same tank, if the capacity of each bucket is 9 litres?

A. 14
B. 15
C. 16
D. 18

Capacity of the tank = (12×13.5)=162 litres
Capacity of each bucket = 9 litres.
Number of buckets needed = 162/9=18