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A concrete planter is formed from a square-based pyramid that was inverted and placed inside a cube.

A. What is the slant height of the pyramid?

B. What is the surface area of the composite figure?

HINT: The surface area consists of lateral faces of the inside of the inverted pyramid and the remaining 5 faces of the cube.

C. How many cubic yards of concrete are needed to make the planter?

A concrete planter is formed from a square-based pyramid that was inverted and placed-example-1

1 Answer

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Answer:

Explanation:

A) To determine the slant height, we would apply Pythagoras theorem to the right angle triangle formed. The opposite side would be the distance from the center of the pyramid to the center of any side. Therefore

Opposite side = 2/2 = 1 yrd

Slant height, L = hypotenuse

Adjacent side = 2 yrd

Hypotenuse² = opposite side² + adjacent side²

L² = 1² + 2² = 5

L = √5 = 2.24 yrds

Slant height = 2.24 yrds

B) Area of each triangular face = 1/2 × 2 × 2.24 = 2.24

Surface area of 4 triangular faces = 2.24 × 4 = 8.96 yrds²

Surface area of the remaining 5 faces of the cube = 5 × 2² = 20 yrds²

surface area of composite figure = 20 + 8.96 = 28.96 yrds²

C) volume = 1/3 × base area × height

Volume = 1/3 × 2² × 2 = 2.67 yrds³

User Abhijith Prabhakar
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