Calculate Cuboid Surface Area: Given Volume 72 cm³ and Length 6 cm

Cuboid Surface Area with Given Volume

Given that the volume of the cuboid is equal to 72 cm³

The length of the cuboid is equal to 6 cm and the height is equal to half the length.

Calculate the surface of the cuboid

666

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Calculate the surface area of the box
00:03 Let's use the formula for calculating box volume
00:10 height times length times volume
00:14 Let's mark the box length as X
00:25 We'll substitute appropriate values and solve for X
00:43 This is the box length
00:51 Let's use the formula for calculating surface area
00:56 2 times (sum of face areas)
01:11 We'll substitute appropriate values and solve for surface area
01:27 Let's solve each multiplication separately
01:44 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given that the volume of the cuboid is equal to 72 cm³

The length of the cuboid is equal to 6 cm and the height is equal to half the length.

Calculate the surface of the cuboid

666

2

Step-by-step solution

The first step is to calculate the relevant data for all the components of the box.

The length of the box = 6

Given that the height of a cuboid is equal to half its length we are able to deduce the height of the box as follows : 6/2= 3

Hence the height = 3

In order to determine the width, we insert the known data into the formula for the volume of the box:

height*length*width = volume of the cuboid.

3*6*width = 72

18*width=72

We divide by 18:

Hence the width = 4

We are now able to return to the initial question regarding the surface of the cuboid.

Remember that the formula for the surface area is:

(height*length+height*width+length*width)*2

We insert the known data leaving us with the following result:

(3*6+4*3+4*6)*2=

(12+24+18)*2=

(54)*2=

108

3

Final Answer

108 cm²

Key Points to Remember

Essential concepts to master this topic
  • Formula: Use V=l×w×h V = l \times w \times h to find missing dimension
  • Technique: Find width: 72 ÷ (6 × 3) = 72 ÷ 18 = 4 cm
  • Check: Surface area = 2(lw + lh + wh) = 2(24 + 18 + 12) = 108 cm² ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to multiply by 2 in surface area formula
    Don't calculate just (lw + lh + wh) = 54 cm² and stop there! This gives only half the surface area because a cuboid has 6 faces (3 pairs). Always multiply by 2 for the complete surface area formula.

Practice Quiz

Test your knowledge with interactive questions

Identify the correct 2D pattern of the given cuboid:

444444999

FAQ

Everything you need to know about this question

Why do I need to find all three dimensions first?

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The surface area formula requires length, width, AND height. Since you only know length (6 cm) and that height = length/2 = 3 cm, you must use the volume formula to find the missing width before calculating surface area.

What does 'surface area' actually mean?

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Surface area is the total area of all faces of the 3D shape. A cuboid has 6 faces: top/bottom, front/back, and left/right sides. Each pair has the same area, so we calculate 3 different areas and multiply by 2.

How do I remember which formula to use when?

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Use V=l×w×h V = l \times w \times h for volume (space inside). Use SA=2(lw+lh+wh) SA = 2(lw + lh + wh) for surface area (covering the outside). Think: volume fills it up, surface area wraps it up!

Can I solve this problem in a different order?

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Yes! You could find height first (6 ÷ 2 = 3), then width (72 ÷ 18 = 4), then surface area. The key is having all three dimensions before using the surface area formula.

What if my volume calculation doesn't give a whole number?

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That's fine! Work with exact fractions or decimals until the final step. Just make sure your arithmetic is careful, especially when the width comes out as a fraction.

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