Mary wants to decorate her tree for Christmas. She wants to put the tree on a wooden block that has a picture of Santa Claus on it and is decorated in colorful paper. She needs to be aware of the precise amount of paper she needs to purchase. if the box measures 80 cm in length, 40 cm in width, and 20 cm in height.

How many square sheets of paper of side 40 cm would she require?

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answer is C.

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Detailed Solution

Given that, the box measures 80 cm in length, 40 cm in width, and 20 cm in height.
We have to find the number of square sheets of paper side 40 cm that she required.
Thus, l = 80 cm, b = 40 cm, h = 20 cm, a = 40.
Surface area of wooden cuboid block is,

S = 2 (l b + b h + h l)

Substitute the values in the formula, we get,

⇒ S = 2 (80 × 40 + 80 × 20 + 40 × 20) cm 2

⇒ S = 2 (3200 + 1600 + 800) cm 2

⇒ S = (2 × 5600) c m 2

⇒ S = 11200 cm 2

To find the area of a square sheet we will use the formula,
Area of square sheet =

a 2

where a is the side of the square.

⇒

A=40

40 cm²

⇒

A=1600 cm²
To find the number of square sheets required to decorate a Christmas tree we will divide the surface area of the wooden block by area of square sheets
Number of square sheets required=