Step-by-step explanation:

Dimension of brick are =20cm×10cm×5cm

volume of 1 brick =20×10×5=1000cm³

Dimension of wall =10m×15m×0.2m

volume of wall =10×15×0.2=30m ³

now no. of brick requried to make wall =

volume of 1 brick / volume of wall

no. of bricks = 1000m³ / 30m³ × 10⁶

= 30 × 10³

[no. of bricks =30,000 bricks.]