Room dimensions

Room dimensions are 5m and 3.5m. The room height is 2.85m. Paint the room (even with the ceiling). There will be two layers. Doors and windows have a total of 2.5 m². One box of paint is enough for 6m². How many boxes of paint are needed? How much do we pay if one box costs 5 €?

Correct answer:

n =  22
x =  110 Eur

Step-by-step explanation:

$$\begin{gathered} a=5\text{m} \\ b=3.5\text{m} \\ c=2.85\text{m} \\ W=2.5{\text{m}}^2 \\ K=6{\text{m}}^2 \\ k=2 \\ S=a\cdot b+c\cdot 2\cdot (a+b)-W=5\cdot 3.5+2.85\cdot 2\cdot (5+3.5)-2.5=\frac{1269}{20}=63\frac{9}{20}=63.45{\text{m}}^2 \\ n=\lceil k\cdot S/K\rceil =\lceil 2\cdot 63.45/6\rceil =22 \end{gathered}$$

$x=5\cdot n=5\cdot 22=110\text{Eur}$

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