Surface Area Comparison: 1x2x3 vs 2x1x3 Rectangular Prisms

Surface Area Calculations with Rectangular Prisms

Are the surface areas of the two orthohedrons below the same or different?

111222333222111333

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Are the surface areas equal?
00:03 Now we'll use the formula for calculating the surface area of a box
00:07 2 times the sum of face areas
00:18 Let's substitute appropriate values for each box
00:50 Let's compare the side values, and we'll see they are equal
00:57 Boxes with equal edges have equal surface areas
01:02 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

Are the surface areas of the two orthohedrons below the same or different?

111222333222111333

2

Step-by-step solution

To solve the problem, we'll proceed through these steps:

  • Step 1: Identify the dimensions of the orthohedrons from the diagram.
  • Step 2: Apply the surface area formula for a cuboid.
  • Step 3: Compare the surface areas to determine if they are equal or different.

Step 1: Dimensions from the diagram:

  • Orthohedron 1: Length l=3 l = 3 , Width w=2 w = 2 , Height h=1 h = 1 .
  • Orthohedron 2: Length l=2 l = 2 , Width w=3 w = 3 , Height h=1 h = 1 .

Step 2: Calculate surface areas using the formula SA=2(lw+lh+wh) SA = 2(lw + lh + wh) .

For Orthohedron 1:
SA1=2(32+31+21)=2(6+3+2)=2(11)=22 SA_1 = 2(3 \cdot 2 + 3 \cdot 1 + 2 \cdot 1) = 2(6 + 3 + 2) = 2(11) = 22 .

For Orthohedron 2:
SA2=2(23+21+31)=2(6+2+3)=2(11)=22 SA_2 = 2(2 \cdot 3 + 2 \cdot 1 + 3 \cdot 1) = 2(6 + 2 + 3) = 2(11) = 22 .

Step 3: Compare the surface areas:
Both orthohedrons have a surface area of 22; therefore, the surface areas are equal.

Thus, the surface areas of the two orthohedrons are equal.

The correct answer is: = = .

3

Final Answer

=

Key Points to Remember

Essential concepts to master this topic
  • Formula: Surface area equals 2(lw+lh+wh) 2(lw + lh + wh) for all rectangular prisms
  • Technique: Calculate each face pair: 2(3×2)+2(3×1)+2(2×1)=12+6+4=22 2(3×2) + 2(3×1) + 2(2×1) = 12 + 6 + 4 = 22
  • Check: Verify by counting all 6 faces and their areas match the formula ✓

Common Mistakes

Avoid these frequent errors
  • Confusing dimensions when rearranged
    Don't think 1×2×3 and 2×1×3 have different surface areas just because dimensions are written differently = wrong comparison! The order of multiplication doesn't change the result since these are the same three dimensions. Always focus on what dimensions you actually have, not their arrangement.

Practice Quiz

Test your knowledge with interactive questions

A cuboid is shown below:

222333555

What is the surface area of the cuboid?

FAQ

Everything you need to know about this question

Why do both prisms have the same surface area even though they look different?

+

Great observation! Both prisms have the exact same three dimensions: 1, 2, and 3. The surface area formula 2(lw+lh+wh) 2(lw + lh + wh) only depends on these values, not how they're arranged.

What does the '2' in the formula mean?

+

The '2' accounts for opposite faces being identical. Every rectangular prism has 6 faces that come in 3 pairs: top/bottom, front/back, and left/right.

Do I need to worry about which dimension is length, width, or height?

+

No! For surface area calculations, it doesn't matter which dimension you call length, width, or height. The formula works with any assignment of the three values.

How can I visualize this to make sure I understand?

+

Think of unfolding the box into a flat pattern. You'll see 6 rectangles: two of each size. Count their areas: 6+6+3+3+2+2=22 6 + 6 + 3 + 3 + 2 + 2 = 22 for both prisms!

What if the prisms were oriented differently in space?

+

Orientation doesn't matter for surface area! Whether a prism is standing up, lying down, or tilted, its surface area stays the same because the faces don't change size.

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Cuboids questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations