Calculate Cube Side Length from 24 cm² Surface Area: Geometry Problem

Surface Area Formulas with Square Root Solutions

The surface area of a cube is 24 cm². How long is the cube's side?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the cube's edge
00:06 In a cube all edges are equal
00:15 The surface area of the cube equals the sum of the faces' areas
01:01 Let's isolate A
01:12 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

The surface area of a cube is 24 cm². How long is the cube's side?

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the given information.
  • Step 2: Apply the appropriate formula for the surface area of a cube.
  • Step 3: Solve the equation to find the side length.

Now, let's work through each step:

Step 1: The problem gives us that the surface area of the cube is 24 cm².

Step 2: We'll use the formula for the surface area of a cube: A=6s2 A = 6s^2 , where A A is the surface area and s s is the side length.

Step 3: Substitute the given surface area into the formula and solve for s s :

6s2=24 6s^2 = 24

Divide both sides by 6 to isolate s2 s^2 :

s2=246=4 s^2 = \frac{24}{6} = 4

Take the square root of both sides to solve for s s :

s=4=2 s = \sqrt{4} = 2

Therefore, the solution to the problem is s=2 s = 2 cm.

3

Final Answer

2 2

Key Points to Remember

Essential concepts to master this topic
  • Formula: Cube surface area equals 6 times side length squared
  • Technique: Divide 24 by 6 to get s2=4 s^2 = 4 , then find square root
  • Check: Verify 6×22=6×4=24 6 \times 2^2 = 6 \times 4 = 24 cm² ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting that a cube has 6 faces, not 4
    Don't use A=4s2 A = 4s^2 = wrong answer of s=6 s = \sqrt{6} ! This treats the cube like it only has 4 faces instead of 6. Always remember a cube has 6 identical square faces, so use A=6s2 A = 6s^2 .

Practice Quiz

Test your knowledge with interactive questions

A cube has a total of 14 edges.

FAQ

Everything you need to know about this question

Why does a cube have 6 faces instead of 4?

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A cube is a 3D shape with faces on all sides: top, bottom, front, back, left, and right. That's 6 faces total, each one a perfect square!

What if I get a decimal when taking the square root?

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Sometimes cube problems give you perfect square roots like 4=2 \sqrt{4} = 2 . If you get a decimal, double-check your arithmetic - many textbook problems are designed to have whole number answers.

Can I solve this without using the square root?

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You must use the square root to find the side length! Once you have s2=4 s^2 = 4 , taking the square root is the only way to isolate the variable s.

How do I remember the surface area formula?

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Think of unfolding a cube - you get 6 identical squares! Each square has area s2 s^2 , so total surface area is 6s2 6s^2 .

What units should my final answer have?

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Since surface area is given in cm², your side length will be in cm (the square root of the area units). Always include units in your final answer!

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