A rectangular container with a base of $200c{m}^2$ is filled with water to a height of $15cm$. If the container has a height of $20cm$, then how much water should be added to fill it completely?

The correct option is A $3l$

Given:
Area of base $=a=200c{m}^2$

Height of container $=20cm$

Volume of the container $=(l\times b)\times h=a\times h=200c{m}^2\times 20cm=4000cm{}^3$

We know that $1000c{m}^3=1l$,
So the capacity of the container is $4l$.

Water is filled to a height of $15cm$.

Volume of filled water in tank $=(l\times b)\times h=200c{m}^3\times 15cm=3000cm{}^3$
So the volume of filled water is $3l$.

Amount of water to be added
$=\text{Capacity of the container}$$-\text{Volume of filled water}$

$\therefore$The quantity of water required to fill the container completely is $1l$.