Cardboard - boxes

The closed cardboard box has the shape of a block measuring 25 cm, 1.2 dm, and 0.5 m. How much cardboard is needed to make 20 such boxes? You need to add 5% to bends.

Final Answer:

S =  9.03 m²

Step-by-step explanation:

$$\begin{gathered} a=25\text{cm}\to \text{m}=25:100\text{m}=0.25\text{m} \\ b=1.2\text{dm}\to \text{m}=1.2:10\text{m}=0.12\text{m} \\ c=0.5\text{m} \\ {S}_1=2\cdot (a\cdot b+b\cdot c+c\cdot a)=2\cdot (0.25\cdot 0.12+0.12\cdot 0.5+0.5\cdot 0.25)=\frac{43}{100}=0.43{\text{m}}^2 \\ n=20 \\ q=100\%+5\%=1+\frac{5}{100}=1.05 \\ S=S_1\cdot n\cdot q=0.43\cdot 20\cdot 1.05=9.03{\text{m}}^2 \end{gathered}$$

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