Final answer:
The maximum volume of a cylindrical tank is 3rs/4 liters. One-third of the tank's maximum volume is correctly calculated as (3rs/4) ÷ (1/3) = 9rs/4.
Step-by-step explanation:
The maximum volume of a cylindrical tank is given as 3rs/4 liters. The question asks for one-third of the tank's maximum volume. To find this, we need to divide the maximum volume by 3. In this case, the correct answer is (3rs/4) ÷ (1/3) = 9rs/4 (option a).