Calculate Cuboid Volume: Surface Area 136 cm³ with 8 cm Length Problem

Surface Area Formula with Missing Dimensions

Given the surface area of the cuboid equal to 136 cm3

Length of the cuboid is equal to 8 cm and the width is equal to half the length.

Calculate the volume of the cube

888

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:12 Let's calculate the volume of the box.
00:15 First, set the length according to the data. Then, solve for the width.
00:25 Great! This is the width of the box.
00:29 Next, we use the formula to calculate the surface area.
00:38 It's 2 times the sum of the face areas.
00:45 Now, insert the values and solve for the height of the box.
01:05 Simply divide by 2.
01:16 Then, isolate H, the height.
01:36 And there you have it, the height of the box.
01:40 Now, let's calculate the box volume.
01:51 Multiply width, height, and length together.
01:55 Insert the values and solve.
02:13 And that's how we find the solution. Well done!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given the surface area of the cuboid equal to 136 cm3

Length of the cuboid is equal to 8 cm and the width is equal to half the length.

Calculate the volume of the cube

888

2

Step-by-step solution

To solve this problem, follow these steps:

  • Step 1: Identify the given information: l=8cm l = 8 \, \text{cm} , w=4cm w = 4 \, \text{cm} , and S=136cm2 S = 136 \, \text{cm}^2 .
  • Step 2: Use the surface area formula to find height h h : 136=2(84+8h+4h) 136 = 2(8 \cdot 4 + 8 \cdot h + 4 \cdot h) .
  • Step 3: Simplify and solve for h h .
  • Step 4: Use the volume formula V=lwh V = l \cdot w \cdot h .
  • Step 5: Substitute the value of h h into the volume formula.
  • Step 6: Calculate and obtain the final result.

Now, let's calculate:

Starting with the surface area equation:

136=2(84+8h+4h) 136 = 2(8 \cdot 4 + 8 \cdot h + 4 \cdot h) .

Simplifying gives:

136=2(32+8h+4h) 136 = 2(32 + 8h + 4h) .

136=2(32+12h) 136 = 2(32 + 12h) .

136=64+24h 136 = 64 + 24h .

Subtract 64 from both sides:

72=24h 72 = 24h .

Divide both sides by 24:

h=3cm h = 3 \, \text{cm} .

Now, calculate the volume using V=lwh V = l \cdot w \cdot h :

V=843 V = 8 \cdot 4 \cdot 3 .

V=96cm3 V = 96 \, \text{cm}^3 .

Therefore, the volume of the cuboid is 96cm3 96 \, \text{cm}^3 .

3

Final Answer

96 cm³

Key Points to Remember

Essential concepts to master this topic
  • Formula: Surface area of cuboid = 2(lw + lh + wh)
  • Method: Find unknown height using 136 = 2(32 + 12h), solve h = 3
  • Check: Volume = 8 × 4 × 3 = 96 cm³ matches surface area ✓

Common Mistakes

Avoid these frequent errors
  • Confusing surface area with volume units
    Don't use cm³ for surface area = wrong formula application! Surface area measures flat covering space (cm²), while volume measures internal space (cm³). Always use surface area formula SA = 2(lw + lh + wh) to find missing dimensions first.

Practice Quiz

Test your knowledge with interactive questions

Calculate the volume of the rectangular prism below using the data provided.

888333222

FAQ

Everything you need to know about this question

Why is the surface area given in cm³ when it should be cm²?

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Good catch! This appears to be a typo in the problem. Surface area should always be in square units (cm²). The calculation still works the same way using SA=2(lw+lh+wh) SA = 2(lw + lh + wh) .

How do I find the width if it's half the length?

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Since length = 8 cm, and width = half the length, then width = 82=4 \frac{8}{2} = 4 cm. Always calculate known dimensions first!

What's the difference between finding height from surface area vs. volume?

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With surface area, you use SA=2(lw+lh+wh) SA = 2(lw + lh + wh) to find the missing dimension. With volume, you'd use V=l×w×h V = l \times w \times h . Surface area considers all 6 faces!

How do I solve 136 = 2(32 + 12h) step by step?

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Step 1: Divide both sides by 2: 68=32+12h 68 = 32 + 12h

Step 2: Subtract 32: 36=12h 36 = 12h

Step 3: Divide by 12: h=3 h = 3 cm

Why do we multiply by 2 in the surface area formula?

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A cuboid has 6 faces that come in 3 pairs of identical rectangles! The formula 2(lw+lh+wh) 2(lw + lh + wh) accounts for both faces of each pair: 2 top/bottom + 2 front/back + 2 left/right.

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