A rectangular grid has 10 rows and 12 columns of square 200 mm tiles, internal joint width 4 mm and uniform grout depth 6 mm. No perimeter joint is included. Model grout area as the complete grid rectangle minus all tile-face areas, so intersections are counted once. Material density is 1.6 kg/L. Add 10% reserve and buy 5 kg bags.
Calculate the whole grout bags to purchase. Keep intermediate values unrounded; round the final answer to 4 decimal places if needed.
