Example exercise: volume and surface area of a cube
We have a cube whose length is 2 cm and we are asked to find its volume and surface area.
Finding the volume of a cube
The volume of a cube is equal to length × width × height.
Since the length, width and height of a cube are all equal, in our case the width and height of our given cube will also be 2 cm. Therefore,
8=2×2×2
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Test your knowledge
Question 1
Look at the cube below.
Do all cubes have 6 faces, equaling its surface area?
Incorrect
Correct Answer:
Yes.
Question 2
All faces of the cube must be?
Incorrect
Correct Answer:
Squares
Question 3
The cube shown below has a base area equal to 36 cm².
Is it possible to calculate the height of the cube? If so, what is it?
Incorrect
Correct Answer:
\( 6 \)
Finding the surface area of a cube
To find the total surface area of a cube, we will first find the surface area of one of its faces and then multiply the result by 6 (remember that cubes are composed of six identical square faces).
The area of each square is 4=2×2
Therefore, the surface area of the cube will be:
4×6=24cm
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Example exercises
Example exercise 1
Given that:
The length of each side of the given cube is equal to 3 cm.
Question:
What is the volume of the cube?
Solution:
The volume of a cube (and the volume of a cuboid) is equal to:
Length × Width × Height
Therefore the volume of the cube: =33=27
Answer:
27cm3
Do you know what the answer is?
Question 1
A cube has a base area of 9 cm².
Is it possible to calculate the volume of the cube? If so, what is it?
Incorrect
Correct Answer:
\( 27 \)
Question 2
A cube has edges measuring 3 cm.
What is the volume of the cube?
Incorrect
Correct Answer:
\( 27 \)
Question 3
Shown below is a cube with a length of 4 cm.
What is the sum of the lengths of the cube's edges?
Incorrect
Correct Answer:
\( 48 \)
Example exercise 2
Given that:
Given a cube in which each face has a surface area of 6 cm.
Assignment:
What is the total surface area of the cube?
Solution:
The total surface area of the cube is the combined area of all of its faces, ie:
Face area
6×6=36
Answer:
36cm2
Example exercise 3
Given that:
In the given cube, the length of each edge is equal to 3 cm.
Question:
What is the length of the diagonal of the face?
Solution:
To solve this question we will use the Pythagorean Theorem to find the length of the diagonal of the face:
A2+B2=C2
Or, in our case:
Edge2+Edge2=Diagonal2
=32+32
=18
18=3×2=diagonal
Answer:
32
Check your understanding
Question 1
The cube shown below has a base area of 16 cm².
Is it possible to calculate the height of the cube? If so, what is it?
Incorrect
Correct Answer:
\( 4 \)
Question 2
How many faces does a cube have?
Incorrect
Correct Answer:
\( 6 \)
Question 3
Given the cube and the length of each edge equals 6.5 cm
What is the sum of the lengths of the edges of the cube?
Incorrect
Correct Answer:
\( 78 \)
Example exercise 4
Given a cube whose edge length is equal to 5 cm.
Task:
Find the volume of the cube.
Solution:
The volume of the cube is equal to the length of the face of the cube to the power of 3
We can write it like this:
53=125
Answer:
125cm3
Example exercise 5
Given a cube whose volume is equal to 112 cm³
Question:
How many whole cubes with a volume of 10 cm³ can fit inside the given cube?
Solution:
We divide the volume of the large cube into 10 to find out how many cubes of 10 cm³ fit into the given cube:
10112=1151
Since we are only asked about whole cubes, it is possible to enter 11 cubes into the cube whose volume is 112 cm³.
Answer:
11 cubes.
Do you think you will be able to solve it?
Question 1
Given the cube whose edge length is equal to 7 cm
What is the sum of the lengths of the edges of the cube?
Incorrect
Correct Answer:
\( 84 \)
Question 2
Given the cube
How many edges are there in the cube?
Incorrect
Correct Answer:
\( 12 \)
Question 3
Find a,b
Incorrect
Correct Answer:
\( a=b=5 \)
Review questions
What is a cube?
A cube is a cuboid with six square, equal faces (all the sides are equal).
How do we find the surface area of a cube?
To find the total surface area of a cube, all we need is the value of one of its sides (since all sides are equal).
Then, we find the surface area of one face by multiplying the side to the power of three.
Lastly, we multiply the surface area of one face by six (since cubes have six equal sides).
Example exercise
Task. Find the total surface area of the following given cube, which has a side length of 7cm
Solution:
Let's start by finding the area of just one face:
Area=7cm×7cm=49cm2
Now, let's multiply the area of one face by six to find the total surface area:
49cm2×6=294cm2
Answer:
=294cm2
Test your knowledge
Question 1
Which of the following figures represents an unfolded cube?
Incorrect
Correct Answer:
Question 2
Is it possible for a cube to have a length equal to the diagonal of the face indicated in the figure?
Incorrect
Correct Answer:
No.
Question 3
A cube has a total of 14 edges.
Incorrect
Correct Answer:
False.
What is the formula used to find the volume of a cube?
The find the volume of a cube, we multiply its three sides.
Remember: since each face is square, all its sides have the same length.
=,×
This formula can also be expressed as:
V=L3
since all the sides are equal.
Finding the volume of a cube: additional practice
Example 1
Task. Find the volume of a cube with a side length of4cm
Solution:
Using our formula, we get:
V=L3
V=(4cm)3=64cm3
Answer
V=64cm3
Example 2
Task. Find the volume of a cube with a side length of 8cm
Solution:
Again, we will use our formula to find the volume:
V=L3
V=(8cm)3=512cm3
Answer
V=512cm3
Do you know what the answer is?
Question 1
Look at the cube below.
Do all cubes have 6 faces, equaling its surface area?
Incorrect
Correct Answer:
Yes.
Question 2
All faces of the cube must be?
Incorrect
Correct Answer:
Squares
Question 3
The cube shown below has a base area equal to 36 cm².
Is it possible to calculate the height of the cube? If so, what is it?
Incorrect
Correct Answer:
\( 6 \)
Examples with solutions for Cubes
Exercise #1
The cube shown below has a base area of 16 cm².
Is it possible to calculate the height of the cube? If so, what is it?
Video Solution
Step-by-Step Solution
To solve this problem, we'll follow these steps:
Step 1: Identify the base area of the cube.
Step 2: Use the formula to find the side length of the base.
Step 3: Recognize that the height of the cube is equal to the side length of the base.
Now, let's work through each step:
Step 1: We are given the base area of the cube as 16cm2.
Step 2: The area of a square is calculated using the formula side2, where "side" is the length of each side of the square.
Setting up the equation: side2=16. Solving for the "side," we find side=16=4cm.
Step 3: Since the cube is a regular geometric shape, the height is equal to the side length of the base. Therefore, the height of the cube is 4cm.
Therefore, the height of the cube is 4cm.
Answer
4
Exercise #2
The cube shown below has a base area equal to 36 cm².
Is it possible to calculate the height of the cube? If so, what is it?
Video Solution
Step-by-Step Solution
To solve this problem, we'll follow these steps:
Step 1: Understand the relationship between the base area and the side length of a cube.
Step 2: Calculate the side length using the square area formula.
Step 3: Conclude that the height of the cube is equal to this side length.
Now, let's work through each step:
Step 1: The basic property of a cube is that all of its three dimensions (length, width, and height) are equal. We know the base area of this cube is given as 36 cm².
Step 2: Using the formula for the area of a square, we have s2=36, where s is the side length of the base.
Solving for s, we find:
s=36=6cm
Step 3: Since all sides of a cube are equal, the height of the cube is also 6cm.
Therefore, the height of the cube is 6cm.
Answer
6
Exercise #3
A cube has edges measuring 3 cm.
What is the volume of the cube?
Video Solution
Step-by-Step Solution
To solve this problem, we'll follow these steps:
Identify the given information: The edge of the cube is 3 cm.
Apply the formula for the volume of a cube: V=a3.
Calculate the volume by substituting the given edge length into the formula.
Now, let's work through each step:
Step 1: The edge length a is 3 cm.
Step 2: The formula for the volume of a cube is V=a3. Substituting the given edge length, we have:
V=33
Step 3: Calculate 33:
3×3×3=27
Therefore, the volume of the cube is 27 cubic centimeters.
Thus, the solution to the problem is 27 cm3.
Answer
27
Exercise #4
A cube has a base area of 9 cm².
Is it possible to calculate the volume of the cube? If so, what is it?
Video Solution
Step-by-Step Solution
To determine if we can calculate the volume of the cube, let's start by analyzing the given information:
The base area of the cube is given as 9cm2. In a cube, each face is a square, so this area corresponds to the area of one face.
To find the side length s of the square face, use the formula for the area of a square: A=s2.
Set up the equation based on the given area: s2=9.
Solve for s by taking the square root of both sides: s=9=3cm.
Now that we have the side length s, calculate the volume V of the cube using the formula for the volume of a cube: V=s3.
Substitute s=3cm into the volume formula: V=33=27cm3.
Therefore, the volume of the cube is 27cm3.
Among the given choices, the correct answer is:
Choice 3: 27
Answer
27
Exercise #5
Shown below is a cube with a length of 4 cm.
What is the sum of the lengths of the cube's edges?
Video Solution
Step-by-Step Solution
To find the sum of the lengths of all the edges of a cube, we can follow these steps:
Step 1: Recognize that a cube has 12 edges, and each edge is the same length.
Step 2: Given the side length of the cube is 4 cm, use the formula for the total edge length.
The formula for the total length of the edges of a cube is:
Total length=number of edges×length of one edge
Substituting the known values, we have:
Total length=12×4cm
Calculating this gives:
Total length=48cm
Therefore, the sum of the lengths of the cube's edges is 48cm.