A cube of side equal to $20 cm$ is open from the top. Its total surface area is _____ $c{m}^2$.

Side of cube = $20 cm$

Since the cube is open on top, its total surface area is equal to $6l^2-l^2=5l^2.$
= $5{\left(20\right)}^2$
= $5\left(400\right)$
= $2000$