Kilograms 4994

The janitor is to paint the computer room walls, which are 7 m long, 5 m wide and 3 m high. The classroom has four square windows with a length of 1 m and a door 1 m wide and 2 m high. At least how many kilograms of paint should he buy if 1 kg of paint passes per 15 m²?

Correct answer:

x =  5 kg

Step-by-step explanation:

$$\begin{gathered} a=7\text{m} \\ b=5\text{m} \\ c=3\text{m} \\ {S}_1=c\cdot (2\cdot a+2\cdot b)=3\cdot (2\cdot 7+2\cdot 5)=72{\text{m}}^2 \\ d=1\text{m} \\ {S}_2=4\cdot d^2=4\cdot 1^2=4{\text{m}}^2 \\ {S}_3=1\cdot 2=2{\text{m}}^2 \\ S=S_1-S_2-S_3=72-4-2=66{\text{m}}^2 \\ s=15{\text{m}}^2 \\ x=\lceil S/s\rceil =\lceil 66/15\rceil =5\text{kg} \end{gathered}$$

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