Paints - one-kilo cans

Mr. Novák is going to paint a shed which is 2.2 m high, 3 m wide, and 4.5 m long. On one side there is a window with dimensions 1*1.2 m. For one coat, 1 kg of paint per m² is used. One-kilogram cans cost 80 Kč, the more cost-effective two-kilogram cans cost 140 Kč. Calculate what is the least Mr. Novák will have to pay if he is going to paint the walls and the door twice, both outside and inside.

Final Answer:

x =  6380 Kc

Step-by-step explanation:

$$\begin{gathered} c=2.2\text{m} \\ a=3\text{m} \\ b=4.5\text{m} \\ {o}_1=1\text{m} \\ {o}_2=1.2\text{m} \\ S=2\cdot (a+b)\cdot c+a\cdot b-o_1\cdot o_2=2\cdot (3+4.5)\cdot 2.2+3\cdot 4.5-1\cdot 1.2=\frac{453}{10}=45.3{\text{m}}^2 \\ m=2\cdot S=2\cdot 45.3=\frac{453}{5}=90.6\text{kg} \\ {m}_1=91\text{kg} \\ 91=2\cdot 45+1 \\ x=\frac{90}{2}\cdot 140+1\cdot 80=6380\text{Kc} \end{gathered}$$

Try another example