Question:

How many bricks, each measuring 25 cm × 11.25 cm × 6 cm, will be needed to build a wall 8 m long, 6 m high and 22.5 cm thick?

(a) 5600

(b) 6000

(c) 6400

(d) 7200

Solution:

(c) 6400

Volume of each brick $=25 \times 11.25 \times 6=1687.5 \mathrm{~cm}^{3}$

Volume of the wall= $800 \times 600 \times 22.5=10800000 \mathrm{~cm}^{3}$

$\therefore$ No. of bricks $=\frac{10800000}{1687.5}=6400$