Answer:
[tex]A=342\ in^2[/tex]
Step-by-step explanation:
Surface Areas
If some surface is made of smaller parts, the total area can be computed as the sum of the particular areas. The area of a rectangle of dimensions a and b is
[tex]A=ab[/tex]
The cereal box is made of 6 rectangles. We'll calculate their areas and then add them to find the total area. For the top and the bottom, we compute twice the area of a rectangle
[tex]A_1=2ab=2(3)(9)=54\ in^2[/tex]
The sides of the box measure 3 inches by 12 inches, their area is
[tex]A_2=2(3)(12)=72\ in^2[/tex]
The front and back of the box measure 9 inches by 12
[tex]A_3=2(9)(12)=216\ in^2[/tex]
The total area of the flattened cereal box is
[tex]A=54+72+216=342\ in^2[/tex]
[tex]\boxed{A=342\ in^2}[/tex]
