Four-sided 7910

The roof of the recreation cottage has the shape of a regular four-sided pyramid with a height of 8m and a base edge of 4m. How much ℅ went to folds and joints, and 75.9 square meters of sheet metal were used to cover the roof?

Correct answer:

p =  15.0528 %

Step-by-step explanation:

$$\begin{gathered} a=4\text{m} \\ h=8\text{m} \\ {h}_2=\sqrt{h^2+(a/2{)}^2}=\sqrt{8^2+(4/2{)}^2}=2\sqrt{17}\text{m}\doteq 8.2462\text{m} \\ {S}_1=a\cdot h_2/2=4\cdot 8.2462/2=4\sqrt{17}{\text{m}}^2\doteq 16.4924{\text{m}}^2 \\ {S}_2=4\cdot S_1=4\cdot 16.4924=16\sqrt{17}{\text{m}}^2\doteq 65.9697{\text{m}}^2 \\ {S}_3=75.9{\text{m}}^2 \\ p=100\cdot \frac{S_3-S_2}{S_2}=100\cdot \frac{75.9-65.9697}{65.9697}=15.0528\% \end{gathered}$$

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