Calculation 43211

The roof is shaped like a hemisphere with a diameter of 8 m. Calculate how much m² of roofing is needed to cover the entire top if we count 15% for waste and residues and round the result to tenths of m². Use the constant pi rounded to two decimal places π=3.14 in the calculation.

Correct answer:

S =  115.6 m²

Step-by-step explanation:

$$\begin{gathered} D=8\text{m} \\ q=100\%+15\%=1+\frac{15}{100}=1.15 \\ r=D/2=8/2=4\text{m} \\ {S}_1=2\pi \cdot r^2=2\cdot 3.1416\cdot 4^2\doteq 100.531{\text{m}}^2 \\ S=q\cdot S_1=1.15\cdot 100.531=115.6{\text{m}}^2 \end{gathered}$$

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