Question:
The paint in a certain container is sufficient to paint on an area equal to $9.375 \mathrm{~m}^{2}$. How many bricks of dimension $22.5 \mathrm{~cm} \times 10 \mathrm{~cm} \times 7.5 \mathrm{~cm}$ can be painted out of this container?
Solution:
The paint in the container can paint the area,
$A=9.375 \mathrm{~m}^{2}$
$=93750 \mathrm{~cm}^{2}$ [Since $1 \mathrm{~m}=100 \mathrm{~cm}$ ]
Dimensions of a single brick,
Length (l) = 22.5 cm
Breadth (b) = 10 cm
Height (h) = 7.5 cm
We need to find the number of bricks that can be painted.
Surface area of a brick
A' = 2 (lb + bh + hl)
= 2(22.5 * 10 + 10 * 7.5 + 7.5 * 22.5)
= 2(225 + 75 + 168.75) = 937.50 cm2
Number of bricks that can be painted = A/A′
= 93750/937.5 = 100
Hence 100 bricks can be painted out of the container.