Brick wall

A garden 70 m long and 48 m wide should surround by a wall 2.1 meters high and 30 cm thick. The bricklayer will build a wall on the garden ground. How many will we need if 300 bricks are required for approximately one m³?

Correct answer:

n =  44378

Step-by-step explanation:

$$\begin{gathered} a=70\text{m} \\ b=48\text{m} \\ c=2.1\text{m} \\ h=30\text{cm}\to \text{m}=30:100\text{m}=0.3\text{m} \\ {S}_1=a\cdot b=70\cdot 48=3360{\text{m}}^2 \\ {S}_2=(a-2\cdot h)\cdot (b-2\cdot h)=(70-2\cdot 0.3)\cdot (48-2\cdot 0.3)=\frac{82239}{25}=3289\frac{14}{25}=3289.56{\text{m}}^2 \\ V=(S_1-S_2)\cdot c=(3360-3289.56)\cdot 2.1=147.924{\text{m}}^3 \\ n=\lceil 300\cdot V\rceil =\lceil 300\cdot 147.924\rceil =44378 \end{gathered}$$

Try another example