Cement and sand for 100 m² plastering numerical

Given: plastering area $= 100\ \text{m}^2$; thickness $= 12$ mm; mix 1:6 (cement : sand).

Step 1: Wet volume of mortar

$$100 \times 0.012 = 1.2\ \text{m}^3$$

Step 2: Dry volume (add 27% for dry bulk, voids in sand and wastage)

$$1.2 \times 1.27 = 1.524\ \text{m}^3$$

Step 3: Cement and sand (sum of ratio $= 7$)

$$\text{Cement} = \frac{1.524}{7} = 0.218\ \text{m}^3 \approx 6.3\ \text{bags (0.0347 m}^3\text{ per bag)}$$ $$\text{Sand} = \frac{6}{7} \times 1.524 = 1.306\ \text{m}^3$$

Answer: Cement = 0.218 m³ (about 6.3 bags of 50 kg = 314 kg); sand = 1.306 m³.