A wall 12 m long, 9 m high and 90 cm thick is to be constructed. Given that one pack contains 450 bricks, how many packs of bricks will be required if each brick is of dimensions 10 cm × 7.5 cm × 7 cm and the cement and sand mixture occupies one-eighteenth volume of the wall? (Rounded off to the nearest integer)

Volume of wall = 12 m × 9 m × 90 cm
Volume of Bricks in wall = (12 m × 9 m × 90 cm) × $$\frac{{17}}{{18}}$$
Let, number of bricks = n
Now, n × 450 × 10 cm × 7.5 cm × 7 cm = (12 m × 9 m × 90 cm) × $$\frac{{17}}{{18}}$$
$$\eqalign{ & {\text{n}} = \frac{{1200 \times 900 \times 90}}{{450 \times 10 \times 7.5 \times 7}} \times \frac{{17}}{{18}} \cr & {\text{n}} = \frac{{160 \times 17}}{7} \cr & {\text{n}} = \frac{{2720}}{7} \cr & {\text{n}} = 388.5 \cr & {\text{n}} = 389{\text{ Answer}} \cr} $$