This question is incomplete and it lacks the attached diagram of the square based pyramid. Find attached to this answer, the square based pyramid.
Correct Question
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. The slant height of the pyramid = 2.24 yards.
B. The surface area of the composite figure = 12.94 square yards.
C. The cubic yards of concrete are needed to make the planter = 2.67 cubic yards.
Step-by-step explanation:
A. What is the slant height of the pyramid?
To calculate the Slant height of a pyramid we make use of the Pythagoras Theorem which is given as:
a² + b² = c²
Where a = Height of the square pyramid represent by h
b = radius of the square pyramid represented by r
c = Slant height of the square pyramid represented by s
Therefore, we have
h² + r² = s²
Looking at the attached diagram, we are given the side length = 2 yards.
The radius of the square based pyramid = side length ÷ 2
= 2÷ 2 = 1 yard.
The height of a square based pyramid = 2 yards
Since , h² + r² = s²
The slant height of the square pyramid is calculated as :
√h² + r² = s
√(2² + 1²) = s
√5 = s
s = 2.24 yards
B. What is the surface area of the composite figure?
We were given hints in the question that the the surface area consists of lateral faces of the inside of the inverted pyramid and the remaining 5 faces of the cube.
Step 1
We find the Lateral area of the faces of the insides of the inverted pyramid
We have 4 faces, Hence,
The formula is given as
a × √( a² + 4h²
a = 2 yards
h = 2 yards
So, = 2 × √( 2² + 4 ×2²
The Lateral area of the faces = 8.94 square yards.
Step 2
Area of the 5 faces of the cube
= a²
Where a = side length = 2 yards
= 2²
= 4 square yards.
Step 3
Therefore, surface area of the composite figure = 8.94 square yards + 4 square yards
= 12.94 square yards.
C. How many cubic yards of concrete are needed to make the planter?
This is calculated by find the Volume of the Square based pyramid.
The formula is given as :
V = (1/3)a²h
Where a = side length = 2 yards
h = height of the square based pyramid = 2 yards
V = 1/3 × 2² × 2
V = 2.67 cubic yards
