Cardboard box

The computer monitor's cardboard box has 75 cm, 12 cm, and 5 dm. How many square cents of the carton are needed to make this box? Add 18 dm² to the folds.

Final Answer:

S =  12300 cm²

Step-by-step explanation:

$$\begin{gathered} a=75\text{cm} \\ b=12\text{cm} \\ c=5\text{dm}\to \text{cm}=5\cdot 10\text{cm}=50\text{cm} \\ {S}_1=18{\text{dm}}^2\to {\text{cm}}^2=18\cdot 100{\text{cm}}^2=1800{\text{cm}}^2 \\ {S}_2=2\cdot (a\cdot b+b\cdot c+c\cdot a)=2\cdot (75\cdot 12+12\cdot 50+50\cdot 75)=10500{\text{cm}}^2 \\ S=S_2+S_1=10500+1800=12300{\text{cm}}^2 \end{gathered}$$

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