Area.

You actually wants to calculate the volume in cubic meters.

Volume for this solid, a cobblestone rectangle, is calculated simply multiplying area of the base by its height.

Replacing the given values in the formula, we get

V = ABh = 90 x 405 x 5 cm3

V = 182250 cm3

Now we convert to cubic meters by dividing by 100x100x100 = 100,000.

V = 182250/100,000 = 1.8225 m3 (cubic meters) (answer)

so, you will need approximately 2 m3 of sand cement mix.

Image from: somatematica.com.br