Grandmother 6375

The Drábekovs inherited a cube-shaped house from their grandmother, which occupied 121 m² of land. They want to insulate the perimeter walls. How many euros will he pay for the material if 1 m² of material costs 11 euros and 15% of the facade area consists of windows and doors?

Correct answer:

x =  4525.4 Eur

Step-by-step explanation:

$$\begin{gathered} S_1=121{\text{m}}^2 \\ a=\sqrt{S_1}=\sqrt{121}=11\text{m} \\ {S}_2=4\cdot S_1=4\cdot 121=484{\text{m}}^2 \\ q=1-\frac{15}{100}=\frac{1\cdot 100}{100}-\frac{15}{100}=\frac{100}{100}-\frac{15}{100}=\frac{100-15}{100}=\frac{85}{100}=\frac{17}{20}=0.85 \\ x=11\cdot q\cdot S_2=11\cdot \frac{17}{20}\cdot 484=\frac{22627}{5}\text{Eur}=4525.4\text{Eur} \end{gathered}$$

Try another example