Examples with solutions for Surface Area of a Cuboid: Identify the greater value

Exercise #1

Look at the two orthohedra below:

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Are the surface areas of the two orthohedra the same or different?

Video Solution

Step-by-Step Solution

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

  • Step 1: Determine the dimensions of each orthohedron from the diagram.
  • Step 2: Calculate the surface area for each cuboid using the formula.
  • Step 3: Compare the calculated surface areas.

Now, let's work through each step:

Step 1: Identify the Given Dimensions
From the visual data, we note that the dimensions of the first orthohedron are given as 1, 2, and 3, while the second orthohedron has the same visual size with similar digits 1, 2, and 3 marked, suggesting identical measurements for each dimension.

Step 2: Calculate the Surface Area for Each Cuboid
Utilize the surface area formula for cuboids:

SA=2(lw+lh+wh) SA = 2(lw + lh + wh)

For Both Orthohedra, Given Dimensions:

  • Length (l l ): 1 unit
  • Width (w w ): 2 units
  • Height (h h ): 3 units

The surface area calculation will be:

SA=2(12+13+23) SA = 2(1 \cdot 2 + 1 \cdot 3 + 2 \cdot 3) =2(2+3+6) = 2(2 + 3 + 6) =211 = 2 \cdot 11 =22 square units = 22 \text{ square units}

As both cuboids have the same dimensions, their surface area calculations yield identical results.

Step 3: Compare Surface Areas
Since both orthohedra compute to the same total surface area of 22 square units, we conclude their surface areas are the same.

Therefore, the solution to the problem is The same.

Answer

The same.

Exercise #2

A new device has been invented: hanging solar panels. The panels are shaped like cuboids so that they can receive sunlight from all directions.

An experiment is conducted and "sunlight" is projected onto the prototypes shown below from all directions.

Which of the two solar panel prototypes will absorb more of the suns energy?

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Video Solution

Step-by-Step Solution

To solve this problem, we'll calculate the surface area of each cuboid solar panel and compare them:

  • Step 1: Identify dimensions for prototype A: length l=70 l = 70 , width w=25 w = 25 , height h=12 h = 12 .
  • Step 2: Calculate the surface area of A using the formula 2(lw+lh+wh)2(lw + lh + wh).
    Surface area =2(70×25+70×12+25×12)= 2(70 \times 25 + 70 \times 12 + 25 \times 12).
  • Step 3: Perform the calculations:
    =2(1750+840+300) = 2(1750 + 840 + 300)
    =2(2890) = 2(2890)
    =5780 = 5780.
  • Step 4: Identify dimensions for prototype B: length l=82 l = 82 , width w=7 w = 7 , height h=13 h = 13 .
  • Step 5: Calculate the surface area of B using the same formula.
    Surface area =2(82×7+82×13+7×13)= 2(82 \times 7 + 82 \times 13 + 7 \times 13).
  • Step 6: Perform the calculations:
    =2(574+1066+91) = 2(574 + 1066 + 91)
    =2(1731) = 2(1731)
    =3462 = 3462.
  • Step 7: Compare the surface areas: 57805780 (A) vs. 34623462 (B).

Therefore, prototype A will absorb more of the sun's energy because it has a larger total surface area.

Thus, the solution to the problem is A.

Answer

A

Exercise #3

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

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Video Solution

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: = = .

Answer

=

Exercise #4

There are two boxes containing a number of balls arranged one on top of the another.

The dimensions of the balls are: 1x1x1.

Assuming that you can see the bottom of the boxes, in which box can you see more balls from the outside?

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Video Solution

Answer

Box B

Exercise #5

A beekeeper has two box hives as shown below.

Each "cell" takes up 0.5 cm² and the entire hive is lined with them.

Which of the hives will have more more cells? How many will there be in it?

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Video Solution

Answer

B: 8x2+240x 8x^2+240x cells