Allowances 82413

The teacher decided to sew covers for the eight-seat blocks in the school library. All cubes are cube-shaped with an edge 40 cm long. How many m² of fabric will the teacher need in total if the blocks are not lined from the bottom, and 5% must be added for seam allowances?

Correct answer:

S =  7 m²

Step-by-step explanation:

$$\begin{gathered} n=8 \\ s=6-1=5 \\ a=40\text{cm}\to \text{m}=40:100\text{m}=0.4\text{m} \\ r=100\%+5\%=1+\frac{5}{100}=1.05 \\ {S}_1=s\cdot a^2=5\cdot 0.4^2=\frac{4}{5}=0.8{\text{m}}^2 \\ {S}_2=n\cdot S_1=8\cdot 0.8=\frac{32}{5}=6.4{\text{m}}^2 \\ S=\lceil S_2\rceil =\lceil 6.4\rceil =7{\text{m}}^2 \end{gathered}$$

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