Question

A cereal box has a length of 8 inches, a width of 2.5 inches and a height of 12 inches. The cereal box is made completely of cardboard. What is the least amount of cardboard needed to make the cereal box?

Answer 1

We know that

[the surface area]=2*[area of the base]+[perimeter of the base]*height
[the surface area]=2*[8*2.5]+[2*(8+2.5)]*12
[the surface area]=40+252-----> 292 in²

the answer is
the least amount of cardboard needed to make the cereal box is 292 in²